BOOKOFABSTRACTS
RSCTHEORETICALCHEMISTRYGROUPCONFERENCEUniversityofNottingham,June20-22,2016
InvitedSpeakers:1-4ContributedTalks:5-15TCGGraduateStudentMeeting:16-25Posters:26-43
1
InvitedSpeaker
InvitedSpeakersHigh-dimensionalquantumdynamicsoffunctionalorganicpolymermaterials:coherenceandcorrelationsatthenanoscale……….2IreneBurghardt(GoetheUniversityFrankfurt)
TaylorseriesexpansionsoftheKohn-ShampotentialNikitasGidopoulos(DurhamUniversity)
Exploringtheactivationmechanismsinligand-gatedionchannelsbyenhancedsamplingmethods……….3CarlaMolteni(King'sCollegeLondon)EvolutionthroughcooperativityinthealkalinephosphatasesuperfamilyLynnKamerlin(UppsalaUniversity)PropertiesandspectraofionicandmolecularliquidsEvaPerlt(UniversityofBonn)Simulatingexcited-statesdynamicsusingtheMCTDHmethod……….4GrahamWorth(UniversityofBirmingham)
2
InvitedSpeaker
High-dimensionalquantumdynamicsoffunctionalorganicpolymermaterials:Coherenceandcorrelationsatthenanoscale
IreneBurghardt1,MatthiasPolkehn1,RobertBinder1andHiroyukiTamura2
1InstituteforPhysicalandTheoreticalChemistry,GoetheUniversityFrankfurt,60438FrankfurtamMain,Germany2WPI-AdvancedInstituteforMaterialResearch,TohokuUniversity,2-1-1Katahira,Aoba-ku,Sendai980-8577,
JapanWepresenthigh-dimensional quantumdynamical studiesofultrafastphotoinducedexciton
migrationanddissociationinfunctionalorganicmaterials,inviewofunderstandingtheintricateinterplayofelectronicdelocalization,coherentnonadiabaticdynamics,andtrappingphenomena.Ashighlightedbyrecentexperiments,quantumcoherencecanplayakeyroleintheelementarytransfersteps,despitethepresenceofstaticanddynamicdisorder.Ourapproachcombinesfirst-principlesparametrizedHamiltonians,basedonTDDFTand/orhigh-levelelectronic structure calculations, with accurate quantum dynamics simulations using the Multi-ConfigurationTime-DependentHartree(MCTDH)method[1]anditsmulti-layerandGaussian-based[2]variants,andaswellasnon-Markovianreduceddynamicstechniques[3].Thistalkwillspecificallyaddress(i)excitondissociationand freecarriergeneration indonor-acceptormaterials, includingmodels forP3HT-PCBMheterojunctions[4,5]andhighlyorderedthiophene-perylenediimideassemblies[6,7],(ii)excitonmultiplicationinacenematerials[8],and(iii)theelementarymechanismofexcitonmigrationaswell as charge-transfer exciton formation in polythiophene and poly-(p-phenylene vinylene) typematerials[9].Specialemphasisisplacedonthespecificinfluenceofmolecularpacking,whichcanactasdeterminingfactorinefficientenergyandchargetransfer.Thepresentedcasestudiesillustratethatthehierarchicalmulticonfigurationalapproachisideallytailoredtovibroniclatticemodelsinmanydimensions.Againstthebackgroundofthesestudies,wewillcommentontheroleoftemporalandspatialcoherence,alongwithaconsistentdescriptionofthetransitiontoaclassicalstatisticalregime.[1]M.H.Beck,A.Jäckle,G.A.Worth,H.-D.Meyer,Phys.Rep.324,1(2000).[2]G.W.Richings,I.Polyak,K.E.Spinlove,G.A.Worth,I.Burghardt,B.Lasorne,Int.Rev.Phys.Chem.,34,265(2015).[3]K.H.Hughes,B.Cahier,R.Martinazzo,H.Tamura,I.Burghardt,Chem.Phys.442,111(2014).[4]H.Tamura,I.Burghardt,J.Am.Chem.Soc.135,16364(2013).[5]M.Huix-Rotllant,H.Tamura,I.Burghardt,J.Phys.Chem.Lett.6,1702(2015).[6]M.Polkehn,H.Tamura,P.Eisenbrandt,S.Haacke,S.Méry,I.Burghardt,J.Phys.Chem.Lett,7,1327(2016).[7]L.Li,P.Eisenbrandt,T.Roland,M.Polkehn,P.-O.Schwartzetal.,Phys.Chem.Chem.Phys.DOI:10.1039/C6CP00644B(2016).[8]H.Tamura,M.Huix-Rotllant,I.Burghardt,Y.Olivier,D.Beljonne,Phys.Rev.Lett.,115,107401(2015).[9]J.Wahl,R.Binder,I.Burghardt,Comput.Theor.Chem.,1040,167(2014).
3
InvitedSpeaker
Exploringtheactivationmechanismsinligand-gatedionchannelsbyenhancedsamplingmethods
CarlaMolteni
King'sCollegeLondon,London,WC2R2LS,UK
E-mail:[email protected]
Pentamericligand-gatedionchannels(pLGICs),embeddedinthemembraneofnervecells,areimportantneuroreceptorsthatmediatefastsynaptictransmission,areinvolvedinseveralneurologicaldisordersandaretargetsitesfordrugsand,ininvertebrates,insecticides.However,wehavelittleideaofhowtheyfunctionatthemolecularlevelduetotheircomplexityandlimitedexperimentalinformation.Wehaveinvestigatedthefirstcrucialstepoftheiractivationmechanism,whichconsistsinthebindingofa neurotransmitter to their extracellular domain, focussing of the prototypical case of theneurotransmitterGABAbinding to the insectRDL receptor,which is linked to the resistance to theinsecticide dieldrin. Using the ``funnel-metadynamics'' computational technique, which efficientlyenhancesthesamplingofboundandunboundstatesusingafunnel-shapedrestrainingpotentialtolimittheexplorationinthesolvent,wehavedescribedthebindingfreeenergylandscape,identifiedthechainofevents leadingGABAfromthesolvent intothebinding-pocketandestimatedthebindingaffinity.Moreover,wehaveshownhowthislandscapeisdisruptedbymutationswhichpreventthereceptortofunction.Wehavealsoassessedthepotentialoftrans-cisprolineswitchforthegatingoftheionchannel,inthecaseofthe5-HT3receptor,whichisactivatedbyserotonin.TheRDLandthe5-HT3receptorssharestructuralandfunctionalfeatureswithotherpLGICs,henceourworkprovidesvaluableprotocolstostudytheactivationmechanismsofpLGICsbeyondconventionaldockingandmoleculardynamicstechniques.
4
InvitedSpeaker
Simulatingexcited-statesdynamicsusingtheMCTDHmethod
GrahamWorth
SchoolofChemistry,UniversityofBirmingham,Edgbaston,B152TT,UKE-mail:[email protected]
To study the time-evolution of photo-excited molecules it is necessary to solve the time-
dependent Schrödinger equation. Theeasiestway todo this conceptually is toexpand thenuclearwavefunctioninabasissetandsolvetheresultingequationsofmotion.Themulti-configurationaltime-dependentHartree(MCTDH)methodisanefficientwaytodothis[1,2]andhasbeenusedinthestudyofavarietyoffundamentalprocesse.Recentcalculationshavebeenusedto,e.g.unravelthesignaloftime-resolvedphoto-electronspectroscopyofpyrrole[3]and identifyanewchargetransferstate inpyrroleclusters[4].Muchoftheeffortforsuchcalculationgoesintocalculatingthepotentialenergysurfaces. In the talk, recent developments of the direct dynamics variational multi-configurationalGaussian(DD-vMCG)method[5,6]willbepresented.Inthesecalculationsthepotentialenergysurfacesarecalculatedon-the-fly,makingthemmorestraightforwardtorun,onlylimitedbytheaccuracyofthequantumchemistrymethodused.
[1]M.Beck,A.Jackle,G.A.Worth,andH.-D.Meyer,Phys.Rep.,2000,324:1–106.[2]G.A.Worth,H.-D.Meyer,H.Koppel,L.S.Cederbaum,andI.Burghardt.Int.Rev.Phys.Chem.,2008,7:569–606.[3]G.Wu,S.P.Neville,O.Schalk,T.Sekikawa,M.N.R.Ashfold,G.A.Worth,andA.Stolow.J.Chem.Phys.,2015,142:074302.[4]S.P.Neville,O.Kirkby,N.Kaltsoyannis,G.A.Worth,andH.H.F.Fielding.NatureComm.,2016,7:11357.[5]G.W.Richings,I.Polyak,K.E.Spinlove,G.A.Worth,I.Burghardt,andB.Lasorne.Int.Rev.Phys.Chem.,2015,34:269–308.
5
ContributedTalk
ContributedTalksSelf-consistentimplementationofmeta-GGAexchange-correlationfunctionalswithintheONETEPlinear-scalingDFTcode……….6JamesC.Womack(UniversityofSouthampton)DFT-basedembeddingmethods……….7FredManby(UniversityofBristol)Artificialnucleicacids:Coupledclustersolvatedelectronicspectroscopyto50µsMDsimulationofAEGIShelices……….8RobertMolt(CardiffUniversity)FasttimedependentDensityFunctionalTheorycalculationsofX-rayabsorptionandemissionspectroscopy……….9NickBesley(UniversityofNottingham)Moleculardynamicsstudyofself-assemblyofaqueoussolutionsofpoly[9,9-bis(4-sulfonylbutoxyphenylphenyl)fluorene-2,7-diyl-2,2’-bithiophene](PBS-PF2T)inthepresenceofpentaethyleneglycolmonododecylether(C12E5)……….10BeverlyStewart(UniversityofCoimbra)Correlationconsistentbasissetsforthegroup1atomsK-Fr……….12GrantHill(UniversityofSheffield)RadicalSAMenzymes-Mechanism,dynamicsandradicalreactionprofiling……….13ChristofM.Jaeger(UniversityofNottingham)Oscillatingchargemigrationbetweenglycinelonepairssilencedbynucleardelocalisation:CASSCFEhrenfestdynamicsstudy……….14IakovPolyak(ImperialCollegeLondon)UranylU-Oylstretchingvibrationsasaquantitativemeasureofequatorialbondcovalency:aquantumchemicalinvestigation……….15AndyKerridge(LancasterUniversity)
6
ContributedTalk
Self-consistentimplementationofmeta-GGAexchange-correlationfunctionalswithintheONETEPlinear-scalingDFTcode
JamesC.WomackandChris-KritonSkylaris
Chemistry,FacultyofNatural&EnvironmentalSciences,
UniversityofSouthampton,Highfield,Southampton,SO171BJ,UKE-mail:[email protected]
IntheKohn-Shamformulationofdensityfunctionaltheory(DFT),thecomplicatedexchangeand
correlationinteractionsofmany-electronsystemsaredescribedbytheexchange-correlationfunctional,Exc[n],forwhichtheexactformisunknown.Numerousapproximateformsforthisfunctionalhavebeendevelopedoverthepastseveraldecades,andarecategorizedintobroadfamiliesbythecharge-density-dependentingredientsusedintheirconstruction.WhiletheLDA(localdensityapproximation)andGGA(generalizedgradientapproximation)familiesusethechargedensity,n,and itsgradient,todescribeexchangeandcorrelationeffects,functionalsfromthemeta-GGAfamilytypicallyalsodependuponthekineticenergydensity,τ.Theuseofτtoconstructexchange-correlationfunctionsallowsthedevelopmentofmoresophisticated, flexibleandaccurate functional forms,butalsopresentsnewchallengesandcomplexitiesfortheirimplementation.Inordertoextendthetheoreticaladvantagesofmeta-GGAfunctionalstolarge-scaleDFTcalculationsonthousandsofatoms,wehaveimplementedsupportforτ-dependentmeta-GGAfunctionalsinONETEP[1],alinear-scalingelectronicstructurepackage.TheONETEPcodeachieveslinear-scalingcomputationalcostwithnear-complete-basis-setaccuracybymeansofauniqueformulationofdensity-matrixDFTinwhichthetotalenergyisdirectlyminimizedwithrespecttoboththedensitymatrixandasetofstrictlylocalized,self-consistentlyoptimized localorbitals (non-orthogonalgeneralizedWannier functions,orNGWFs).The self-consistent implementation of meta-GGA functionals within the linear-scaling formalism ofONETEP presented some significant challenges, requiring detailed consideration of the effect of τ-dependenceonthegradientofthetotalelectronicenergy,andtheformoftheτ-dependentexchange-correlationpotentialintermsoftheNGWFsusedinONETEP.Inthiswork,wepresentthetheoreticalinnovationsnecessarytoimplementτ-dependentmeta-GGAfunctionalsforuseinself-consistentlinear-scalingDFTcalculationsusingONETEP.Wealsopresentthevalidationoftheaccuracyoftheimplementedmeta-GGAfunctionalsanddemonstratethecomputationalscalingofourapproach.[1]C.-K.Skylaris,P.D.Haynes,A.A.Mostofi,andM.C.Payne,J.Chem.Phys.,2005,122,084119.
7
ContributedTalk
DFT-basedembeddingmethods
FredManby
BristolUniversitySchoolofChemistry,EnglandE-mail:[email protected]
Variousquantumembeddingtechniques,inwhichonequantummechanicalleveloftheoryis
embedded in another, are emerging as powerful tools for extending thedomainof applications inquantumchemistry.InthistalkIwillsurveysomeofthekeydevelopments,anddescribevariouseffortsin our own group to developmethods that allow embedding of high-accuracy electronic structuremethods in density functional theory, and extension of quantum chemistry to condensed-phaseproblems.
8
ContributedTalk
Artificialnucleicacids:Coupledclustersolvatedelectronicspectroscopyto50μsMDsimulationofAEGIShelices
RobertMolta,b,JasonByrdc,MillieGeorgiadisd,andNigelRichardsa
aSchoolofChemistry,CardiffUniversity,ParkPlace,Cardiff,CF104AT,UK
bDepartmentofChemistryandChemicalBiology,IndianaUniversity-PurdueUniversityIndianapolis,IN,46202,USAcDepartmentofChemistry,QuantumTheoryProject,UniversityofFlorida,GainesvilleFL32611,USA
dDepartmentofBiochemistry&MolecularBiology,IndianaUniversitySchoolofMedicine,Indianapolis,IN,46202,USA
E-mail:[email protected]
We present the physical chemistry underlying several artificial nucleic acids from ab initiofragmentcoupledclustercalculationsto50μsMDcalculationsofAEGISDNAhelices.Artificialnucleicacidshavebeenexpandinginutility,capableofformingstableDNAhelicesexperimentally,andrepresentapromisinghorizonoffuturegeneticmanipulation.Ourstudiesrangefromestablishingthepropertiesofindividual nucleic acids, quantifying the dispersion of their stacking interactions, establishing thetautomericequilibriaviacalculatedelectronicspectroscopyinsolution,andobservingthemacroscopicDNAhelicaleffectsoftheunusualdispersioninteractionsofartificialnucleicacids.Thisworkservestoadvancefragmentedcoupledclustermethodologyaswellasgiveinsighttothechemistrygoverningsyntheticbiology.
9
ContributedTalk
Fasttime-dependentDensityFunctionalTheorycalculationsofX-rayabsorptionandemissionspectroscopy
NicholasA.Besley
SchoolofChemistry,UniversityofNottingham,UniversityPark,Nottingham,NG72RD,UK
E-mail:[email protected]
AdvancesinexperimentaltechniqueshaveprovidedX-rayspectroscopywithamuchgreaterrichnessinstructureandtheabilitytoprobechemicalprocessesonanultrafasttimescale.Quantumchemicalcalculationsoftenplayakeyroleintheanalysisofexperimentaldataanditisimportantthatthecomputational methodology progresses alongside experiment. In this talk the calculation of X-rayabsorptionandemissionspectroscopyusingtime-dependentdensityfunctionaltheorywillbeoutlined.Recentprogresstoimprovetheefficiencyandspeedofthesecalculationsandtheirextensiontolargesystemswillbedescribed.
10
ContributedTalk
Moleculardynamicsstudyofself-assemblyofaqueoussolutionsofpoly[9,9-bis(4-sulfonylbutoxyphenylphenyl)fluorene-2,7-diyl-2,2’-bithiophene](PBS-PF2T)inthepresenceofpentaethyleneglycol
monododecylether(C12E5)
BeverlyStewart,HughDouglasBurrows
CentrodeQuímicadeCoimbra,ChemistryDepartment,UniversityofCoimbra,3004-535,Coimbra,PortugalE-mail:[email protected]
Thehighefficienciesobservedinphotosyntheticlightharvestingsystemsarearesultoftheir
elegantself-assembledstructures.Inordertomimicthesestructuresinsyntheticsystemsitisrequiredtobothcontrolandunderstandaggregation.Heretheuseofcomputationaltechniquesispresentedasamethodbywhichtoobservethebehaviourofasmallfluoreneconjugatedpolymerstructure[1].InterestliesprimarilyinthestudyofanionicPBS-PF2T[2]anditsobservedaggregationbehaviouraswellasthesignificanceofsurfactantpresenceuponthisaggregation.DynamicsimulationshavethusfarindicatedthataggregationofPBS-PF2T,andrelatedconjugatedpolyelectrolytes,isinhibitedinthepresenceofnon-ionicoxyethylenebasedsurfactantsCmEn[3],bywayofseparatingthepolymersandencapsulatingtheminliquidcrystallinesurfactantphases.HeretheeffectsofpentaethyleneglycolmonododecyletherC12E5,isinvesitgatedasanaggregationinhibitor.
Figure1.PBS-PF2TencapsulatedbyC12E5.Theimportanceofvariousinter-andintra-molecularinteractions,aswellassolventtemperature,willbediscussedascontributingfactors intheproductionofwell-definedaggregatedstructures.Byusingacomputationalapproachitispossibletodevelopanunderstandingofhowspecificfactorsaffectboththestructures and properties of aggregated systems and attempt to produce specific self-assembled
11
ContributedTalk
structureswhichmayoptimise theefficiencyofenergyandelectron transferprocesses in syntheticarchitectureswhichmimicthenaturalphotosyntheticlightharvestingcomplex.[1]Burrows,H.D.Tapia,M.J.Fonseca,S.M.Pradhan,S. Scherf,U.Silva,C.L.Pais,A.C.C.Valente,A.J.M.Schillén.K.Alfredsson,V.Carnerup.M.Tomišič,M.andJamnik,A.Langmuir2006,25,5545-5556.[2]Knaapila,M.Fonseca,S.M.Stewart,B.Torkkeli,M.Perlich,J.Pradhan,S.Scherf,U.Castro,R.A.E.andBurrows,H.D.SoftMatter,2014,10,3103-3111.[3]Burrows,H.D.Fonseca,S.M.Silva,C.L.Pais,A.C.C.Tapia,M.J.Pradhan.S.andScherf,U.Phys.Chem.Chem.Phys,2008,10,4420-4428.
12
ContributedTalk
Correlationconsistentbasissetsforthegroup1atomsK–Fr
J.GrantHill
DepartmentofChemistry,UniversityofSheffield,BrookHill,SheffieldS37HF,UKE-mail:[email protected]
Thecorrelationconsistentfamilyofbasissetsseealotofuseinhigh-accuracyabinitioquantum
chemistry [1,2],partlydue to their regularenergetic convergencecharacteristics leading toefficientcompletebasissetlimitextrapolationtechniques.Developmentsinultracold(<1mK)chemistrymeansaccuratecalculationsonmoleculescontainingheavyalkalimetals,suchasRbCs[3]areofinteresttoboththeoreticalandexperimentalgroupsworkinginthisarea,yetthereisalimitedchoiceofbasissetsforsuchmolecules.Withthismotivation,thedesignofcorrelationconsistentbasissetsforthegroup1atomsK–Frwillbepresented.Basissetstobeusedinconjunctionwithsmall-corepseudopotentialsoftheStuttgart-Masseyvariety[4],denotedcc-pVnZ-PP(n=D,T,Q,5),havebeenoptimisedalongwithall-electronDouglas-Krollsets,cc-pVnZ-DK(n=D–Q).Thesebasissetscanalsobeaugmentedwithdiffusefunctionsforthecalculationoflong-rangeinteractions,andwithadditionalfunctionsforthedescriptionofcore-valencecorrelation.ThevalidationoftheresultingbasissetsonthediatomicsM2,MHandMF(M=K,Rb,CsandFr),attheCCSD(T)leveloftheory,willalsobedescribed.Itisevidentthatcorrelationoftheoutercoreelectronsisvitalforcomputedspectroscopicconstantstoapproachexistingexperimentaldata.
[1]T.H.Dunning,Jr,J.Chem.Phys.,1989,90,1007-1023.[2]J.G.Hill,Int.J.QuantumChem.,2013,113,21-34.[3]P.K.Molony,P.D.Gregory,Z.Lietal.,Phys.Rev.Lett,2014,113,255301.[4]I.S.Lim,P.Schwerdtfeger,B.MetzandH.Stoll,J.Chem.Phys.,2005,122,104103.
13
ContributedTalk
RadicalSAMenzymes–Mechanism,dynamicsandradicalreactionprofiling
ChristofM.Jaegera,DamianoSpadoniaCharlesLaughtonbandAnnaK.Crofta
aDepartmentofChemicalandEnvironmentalEngineering,FacultyofEngineering,
UniversityofNottingham,UniversityPark,Nottingham,NG72RD,UKbFacultyofScience,UniversityofNottingham,UniversityPark,Nottingham,NG72RD,UK
E-mail:[email protected]
Enzymes capable of controlling radicals present and wide range of radical-dependentmechanisms,with potential for applications inmedicinal and synthetic chemistry. The radical SAMenzymefamilyusesS-adenosylmethionine(SAM)asco-substrateorcofactortogenerateradicalsdirectlywithintheprotein.Whileageneralframeworkforthisinitialcatalyticmechanismhasbeenestablishedoverthepastyears,[1]muchlessisknownaboutthesubsequentchemicalrearrangementsinmostcases.Understandingofthesemechanismscanbeenhancedthroughtheuseofcomputationalapproaches.BesidesdetailedfullQM/MMmethods,combinedmoleculardynamicsand‘snapshot’(e.g.electronicstructure)methodscangivehighlybeneficiousinsightscomplementingoneanother.WepresentrecentresultsillustratinghowsuchcomputationalapproachescanbeusedtoshedlightontheradicalcontrolmechanismsutilisedinradicalSAMenzymes,particularlywithaviewtounderstandinghowtheseenzymesmightbothfacilitatedesiredconversionsandpreventunwantedsidereactions.Wealsofocusontheproblemthattheneedofthisdeeperunderstandingisalsothebottleneckforamore rapid access to rational enzyme design.Wewill show how radical reaction profiling throughcalculatingradicalstabilisationenergies(RSEs)[2]offersanattractivepossibilitytoassesschangesoftheoverall thermodynamicsof radical rearrangements as central steps in radical SAMenzymecatalysisthrough theexampleof the recently structurally resolvedbacterial7-carboxy-7-deazaguanine (CDG)synthase(QueE).[3]Acombinationofmoleculardynamics(MD)simulationsandquantummechanical(QM)calculationshasprovidednewinsightsintothemechanismofhowtheQueEenzymecontrolsitsradicalrearrangement,whichinvolvesaveryinterestingring-contractionstepandadditionalmetalcationbindingthatinfluencesthecatalysis.[4][1]J.B.Broderick,etal.,Chem.Rev.,2014,114,4229.[2]J.HioeandH.Zipse,.FaradayDisc.,2010.145,301.[3]D.P.Dowling,etal.,Nat.Chem.Biol.,2014,10,106[4]R.M.McCartyandV.Bandarian,Bioorg.Chem.,201243,15.
14
ContributedTalk
Oscillatingchargemigrationbetweenglycinelonepairssilencedbynucleardelocalisation:CASSCFEhrenfestdynamicsstudy
IakovPolyak,AndrewJenkins,MorganeVacher,MichaelJ.BearparkandMichaelA.
Robb
FacultyofNaturalSciences,DepartmentofChemistry,ImperialCollegeLondon,SouthKensingtonCampus,London,SW72AZ,UK
E-mail:[email protected]
Recent advances in attosecond spectroscopy enabled a deeper insight into the electrondynamics following ionisation of molecules. Accordingly, theoretical studies in this field becomeincreasinglyimportant.Oneofthetime-dependentmethodsofchoiceisEhrenfestdynamics,andinourgroupwedevelopedasecond-orderEhrenfestdynamics,usingcompleteactivespaceself-consistentfield(CASSCF)toobtainaccuratetime-dependentelectronicwavefunctionsandcorrespondingenergieson-the-fly [1], which has been successfully used to study electron dynamics both at frozenmoleculargeometriesandcoupledtothedynamicsofnuclei.Animportantissuetoinvestigateisdecoherenceofelectrondensityoscillationsupon ionisation–ability topredictdecoherence isvital fordesigninganexperiment.Previouslywehaveshownthatchargeonglycinelonepairscoherentlyoscillateswithoutsignificantinteractionwithnuclearmotion[2].Inthecurrentworkourstudyrevealsfastdecoherenceofchargemigrationinglycinethathappensifappropriatesamplingoftheinitialnuclearwavepacketistakenintoaccount.Weinvestigatetheeffectofthechosenactivespaceonthefinalresultsaswellastrytogetinsightintothewaytheinitialwavepacketshouldbeconstructedtoprovideanaccuratedescriptionofelectrondynamics.
[1]M.Vacher,D.Mendive-Tapia,M.J.BearparkandM.A.Robb,Theor.Chem.Acc.,2014,133,1505.[2]M.Vacher,M.J.BearparkandM.A.Robb,J.Chem.Phys.,2014,140,201102.
15
ContributedTalk
UranylU-Oylstretchingvibrationsasaquantitativemeasureofequatorialbondcovalency:aquantumchemicalinvestigation
PoppyDiPietro1,AndyKerridge2
1DepartmentofChemistry,UniversityCollegeLondon,20GordonStreet,London,WC1H0AJ,UK
2DepartmentofChemistry,LancasterUniversity,Lancaster,LA14YB,UKe-mail:[email protected]
Theconceptofcovalencycanbeinterpretedinmanyways,anddifferentinterpretationsmay
leadtocontradictoryconclusions.Theoreticalapproachestounderstandingcovalentcontributionstobondingtypicallyemployeitheri)orbital-basedorii)density-basedanalysismethods1-2.Thecomplicatedelectron structure of actinide complexes, present due to the combined effects of relativity, strongelectron correlation andweak interactions with ligand fields can render orbital-based approachesambiguousbutthisinitselfisn’tjustificationforthevalidityofdensitybasedapproaches.
Hereweconsiderarangeofmodeluranylcomplexesanddemonstratethatcomplementarydescriptionsof covalent contributions to bonding derived from density based analyses are commensuratewithvariation in binding energies3. Furthermore, we demonstrate strong correlations between thesemeasuresandcalculatedU-Oylvibrationalfrequencies indicatingthat, inthesesystemsat least,suchvibrationscanbeconsideredaquantitativemeasureofequatorialbondcovalency.
Figure1.Densitydifferenceplotsandanalysisofthereduceddensitygradientof[UO2(NC)5]3-
[1]A.Kerridge,DaltonTrans.,2013,42,16428[2]A.Kerridge,RSCAdv.,2014,4,12078[3]P.DiPietroandA.Kerridge,Inorg.Chem.,2016,55,573
16
TCGGraduateStudentMeeting
TCGGraduateStudentMeetingExplicitlycorrelatedtreatmentoftransitionmetalcontainingsystems:Anongoingeffort……….17StellaKritikou(UniversityofSheffield)Quantumdynamicswithadaptivebasissetsandshort-timetrajectories……….18MaximilianA.C.Saller(UniversityofWarwick)PropertiesofBimetallicAuAgNanoparticlesforH2Production……….19AnnaGould(UniversityCollegeLondon)Capturingstaticcorrelationeffectswithoutusingmulti-referencemethods……….21JoshuaBlack(CardiffUniversity)Latticevibrationsinmolecularcrystals:polymorphismandphasetransitions……….22JonasNyman(UniversityofSouthampton)SinglebaseflippingmechanismsandkineticsinaDNAduplex:anenergylandscapeperspective……….23DebayanChakraborty(UniversityofCambridge)Applyingdirectquantumdynamicstophoto-excitedprocesses:Protontransferandchargemigration……….24ErynSpinlove(UniversityofBirmingham)Aninvestigationintocompetitionbetweenhalogenbondingandhydrogenbondinginmicrosolvated1-methyl-5-halouracil……….25SimonW.L.Hogan(UniversityofStAndrews)
17
TCGGraduateStudentMeeting
Explicitlycorrelatedtreatmentoftransitionmetalcontainingsystems:Anongoingeffort
StellaKritikouandJ.GrantHill
DepartmentofChemistry,UniversityofSheffield,BrookHill,SheffieldS37HF,UK
E-mail:[email protected]
Theexplicitlycorrelated(F12)abinitiomethodssignificantlyreducethebasissetdemandsofhigh-accuracy quantum chemistry, enabling meaningful coupled cluster and multi-referenceconfigurationinteractioncalculationstobecarriedoutonamuchwiderrangeofsystems.Advancesinbasis setsdesigned specifically foruse inF12calculationshavepushed thiseven further. ThereareexamplesintheliteratureofF12methodsnowbeingusedtoinvestigatetransitionmetalcomplexes,whichhastypicallybeenthereserveofdensityfunctionaltheory.Theaccuracyofexplicitlycorrelatedcoupledclustermethodsfor3dtransitionmeta-containingmoleculeswillbedemonstratedthroughanalysisofgeometriesandatomisationenergiesofarecentlyproposedtest set [1]. Comparison with experimental and composite thermochemistry derived data revealsacceleratedconvergencethatwilltranslatetosignificantcomputationalsavings.Nonetheless,explicitlycorrelatedcalculationsusingexistingbasissetsdonotalwaysconvergesmoothly,removingsomeoftheattractionofusingwavefunction-basedmethods.Inordertotacklethisproblem,correlationconsistentbasissetsforthe4dtransitionmetalelementsY-PdhavebeendevelopedandoptimisedspecificallyforusewithF12methods.Thesesetsaredesignedwithefficiencyandsmoothconvergenceinmind,andtheyholdthepromiseofaccuratecalculationsontransitionmetal-containingcomplexesofachemicallyrelevantsize.[1]X.Xu,W.Zhang,M.TangandD.G.Truhlar,J.Chem.TheoryComput.,2012,11,2036-2052.
18
TCGGraduateStudentMeeting
Quantumdynamicswithadaptivebasissetsandshort-timetrajectories
MaximilianA.C.SallerandScottHabershon
DepartmentofChemistry,WarwickUniversity,Coventry,CV47AL
CentreforScientificComputing,WarwickUniversity,Coventry,CV47ALE-mail:[email protected]
The computational study of the quantum dynamics of non-trivial systems heavily relies on
efficientexpansionoftheinherentlycomplex,multidimensionalwavefunctiontofacilitatepropagationintime.Atpresent,basissetsemployedinquantumdynamicssimulationsgenerallyfallintooneoftwoclasses.Basissetswhich,afterhavinginitiallybeendistributedinphasespace,remainconstantthereafter,withtimepropagationbeingsolelyexpressedthroughvariationofasetofexpansioncoefficients,arecommonly referred to as being “time-independent”. Conversely, if basis functions are propagatedthroughphasespacealongsidetheircoefficients,theresultingbasissetistermed“time-dependent”.
Whiletheaforementionedstrategieshavebeenemployedinnumerous,successfulquantumdynamicssimulations,theybothcarrywiththemaninherentsetofdrawbacks[1].Duetotheirstaticnature,time-independentbasissetsmuststrivetodescribethewavefunctionacrossallofphasespaceatalltimes,basedonlyontheinformationavailableduringtheirinitialsampling.Inpractice,thisresultsinverylargebasissets,spanningallofrelevantphasespaceinagrid-likemanner,leadingtounfortunateexponentialscaling.Time-dependentbasissets,whileenabledbytheirdynamiccharactertoremainsmallerinsize,can violate energy conservation laws unless propagated using variational equations of motion.Furthermore,basisfunctionpropagationcansuffergreatlyfromnumericalill-conditioning.
Inarecentpublication[2],weintroducedanovelapproachtobasissetsamplingcapitalisingontheadvantagesofbothaforementionedstrategies,whileavoidingtheirdrawbacks.Wesamplephasespaceusing a set of trajectories to selectively place basis functions in regions relevant to wavefunctionpropagation.Treatingtheresultingbasissettime-independentlyyieldedveryencouragingresultsfortwochallengingbenchmarkproblems,namelytherelaxationdynamicsofphoto-excitedpyrazineandtheSpin-BosonHamiltonian.
Wearecurrentlyaimingtoaddressthekeyassumptionofthistechnique,namely,thevalidityofclassicaltrajectoriesasanapproximationtoquantumdynamics,whichisknowntoonlybesoundintheshorttimelimit.Wesubmitthatshortburstsoftrajectorysamplingwillresultinasmall,highlyaccurateadaptivebasisset,resampledandoptimizedviathematchingpursuitalgorithm.[1]S.Habershon,J.Chem.Phys.,136014109(2012)[2]M.A.C.Saller,S.Habershon,J.Chem.Theo.Comput.,118(2015)
19
TCGGraduateStudentMeeting
PropertiesofbimetallicAuAgnanoparticlesforH2production
AnnaGouldab,AndrewJ.LogsdailbandC.RichardA.Catlowb
aUKCatalysisHub,ResearchComplexatHarwell,Oxon,Didcot,OX110FA,UKbKathleenLonsdaleMaterialsChemistry,DepartmentofChemistry,UniversityCollegeLondon,20GordonStreet,
London,WC1H0AJ,UKE-mail:[email protected]
Bimetallicnanoclusters(“nanoalloys”)arenanometre-sizedaggregatesthatexhibitdistinctive
properties from those associatedwith single atomsorbulkmatter.A varietyof sizes and chemicalarrangements are possible for nanoalloys, making them suitable for widespread application inengineering,magnetism,andcatalysis;Au−Agnanoalloyshavebeenshowntoimprovereactionturnover,incomparisontomonometallicalternatives,whenusedasco-catalystsforphotocatalyticH2production.Inthepresentedwork,wehaveinvestigatedthethermodynamicandkineticstabilityof147-atomAu-Agnanoalloys,asafunctionoftheirchemicalorderingandcomposition,usingdensityfunctionaltheory(DFT)and interatomic potentials (IPs). We determined the most thermodynamically stable chemicalarrangementsfordifferingAu:Agratios,andtheirelectronicpropertieswereevaluatedwithrespecttothephotocatalyticH2evolutionreaction[1].Wehavealsoexaminedtheinfluenceofheatingprocessesonthenanoclusters,ascalcinationproceduresareoftenrequired inexperimenttoremovecappingagentssuchaspolyvinylpyrrolidone(PVP).Thenanoclusterswereheatedfrom0–900K(NVT)usingIPmoleculardynamicsandweobservedlowtemperaturediffusionofAgcoreatomstothesurfaceforAg@Au (core@shell) nanoparticles, resulting in a pseudo-spherical geometry and altered chemicalproperties(Fig.1).ThislowtemperaturediffusionmayexplainwhytherearefewsuccessfulexperimentalreportsofAg@Ausynthesis,incomparisontoAu@Ag,asweillustratethatthestabilityofthischemicalarrangementsishighlydependentonshellthickness[2].Finally,wealsostudytheadsorptionofmolecularintermediariesonthenanoparticles,determiningtheirbindingstrengthandpossiblereactivity.TheCOmoleculeisofparticularinterest,asthiscanbeusedasaprobemoleculeexperimentally;IRstretchingfrequencyshiftsoftenreflectchangesinthenanoparticlemorphology or chemical arrangements. The calculated CO frequencies are compared with in situexperimental data, obtained from combined extended X-ray absorption fine structure and diffusereflectanceinfraredspectroscopy(EXAFS/DRIFTS).
20
TCGGraduateStudentMeeting
[1]A.L.Gould,C.J.Heard,A.J.Logsdail,C.R.A.Catlow,Phys.Chem.Chem.Phys.2014,16,21049-21061.[2]A.L.Gould,A.J.Logsdail,C.R.A.Catlow,J.Phys.Chem.C.2015,119,23685-23697.
21
TCGGraduateStudentMeeting
Capturingstaticcorrelationeffectswithoutusingmulti-referencemethods
JoshuaBlack
SchoolofChemistry,CardiffUniversity,MainBuilding,
ParkPlace,Cardiff,CF103AT,UKE-mail:[email protected]
Coupledclustertheoryisnowwidelyusedincomputationalchemistry,withCCSD(T)oftenbeingthedefactostandardforthecalculationofvariousmolecularproperties.Thisisduetoitssuccessincapturingthedynamicelectroncorrelationeffects.However,whenstaticcorrelationstartstobecomeimportantwithinasystem,suchasintransitionstatesandradicalmolecules,traditionalcoupledclustertheorycanproduceerroneousandunreliable results.Weproposeamethod,Quasi-Variational coupled clustertheory,whichisabletocapturebothdynamicandstaticeffects.Withour'blackbox'method,wecantheninvestigatethesechallengingchemicalsystemswithouttheneedtousetheexpensiveanddifficultmulti-referencemethods
22
TCGGraduateStudentMeeting
Latticevibrationsinmolecularcrystals:Polymorphismandphasetransitions
JonasNymanandGraemeM.Day
SchoolofChemistry,UniversityofSouthampton,UniversityRoad,Southampton,SO171BJ,UK
E-mail:[email protected]
Itispossibletopredicthowmoleculeswillcrystallisebyperforminganexhaustivesearchofallpossiblemolecularpackingalternativesandidentifyingthemostenergeticallyfavourablepackings.Thedevelopment of methods for Crystal Structure Prediction (CSP) is a rapidly growing field withincomputationalchemistry.Themostcommonmethodsrelyoncomputingthecohesiveenergybetweenthemolecules,whileignoringeffectsduetotemperatureandpressure.Latticevibrationalcalculationscanbeusedtoaccountforthermalcontributionsandhencehavethepotentialofimprovingtheoutcomeof crystal structure predictions and may reveal the temperature-dependence of the stabilities ofalternativecrystalforms,seeFig.1.
Figure1.Calculatedquasi-harmoniclatticefreeenergyofthreepolymorphsof2,2’-dipyridylamine(CSDref.DPYRAM).Wehaveimplementedcomputationallyveryefficientmethodsthatfacilitatelargescaleapplicationofharmonicandquasi-harmoniclatticedynamicstohundredsofpolymorphpairsortoentirelandscapesofpredictedcrystalstructures[1,2].Abenchmarkedandhighlyaccurateanisotropicforcefieldisusedtoperformrigid-moleculevibrationalcalculationstoobtainGibbsfreeenergiesofmolecularcrystals[3].Specialcareistakenindealingwithphonondispersioninawayrarelyaffordablewithelectronicstructuremethods.Ipresentresultsdemonstratingthatpolymorphsoforganicmolecularcrystalshaveverysmallenergy-andentropydifferences,whichhasimportantconsequencesforthepredictionanddevelopmentofmolecularmaterials.Inaddition,Idiscusstheimportanceofaccountingforthermalexpansionandtheprospectsofpredictingphasetransitions.
[1]J.Nyman,G.M.Day,CrystEngComm,2015,17,5154-5165[2]J.Nyman,G.M.Day,(inpreparation)[3]J.Nyman,O.SheehanPundyke,G.M.Day,(submitted)
23
TCGGraduateStudentMeeting
SinglebaseflippingmechanismsandkineticsinaDNAduplex:anenergylandscapeperspective
DebayanChakraborty,KaushikSenandDavidJ.Wales
DepartmentofChemistry,UniversityofCambridge,LensfieldRoad,CB21EW,UnitedKingdom
Email:[email protected]
BaseflippingisanelementaryandlocalizeddeformationofaDNAfragment,initiatedbytheruptureofWatson-Crickinteractionsatatargetbase-pair,followedbyextrusionofoneofthebasestoanextrahelicalposition.Onextrusion,thegeneticinformationotherwiseencoded,becomesaccessibletoenzymes.InmanyimportantcellularprocessessuchasDNAtranscriptionandreplication,baseflippingconstitutesakeystep.Inaddition,thereisgrowingevidencetosuggesttheimportanceofbaseflippinginDNAdamagerecognitionbyrepairenzymes.Despiteawealthofexperimentalandtheoreticalstudies,themicroscopicdetailsofbaseflippingmechanismsandkineticsarenotclearlyunderstood.Inthiswork,weemploytheDiscretePathSamplingmethodinconjunctionwithanall-atompotentialandanimplicitsolventmodeltoinvestigatetheflippingmechanismsandkinetics inaB-DNAduplex, intermsof itsunderlyingenergylandscape.Wefindthatbaseflippingcanoccureitherviathemajororminorgrooves,inagreementwithprevioussimulations.Furthermore,theflippingtimescalesareestimatedtobeinthemillisecondregime,consistentwithimino-protonexchangeexperiments.Ourresultsalsodemonstratethatevenforlocaldeformationssuchasbase-flipping,aperfectstructuralorderparametermaynotexist,andthereforehighlightthepitfallsofusinglow-dimensionalprojectionsoftheenergylandscape.
24
TCGGraduateStudentMeeting
Applyingdirectquantumdynamicstophoto-excitedprocesses:Protontransferandchargemigration
KaiteErynSpinloveandGrahamWorth
SchoolofChemistry,CollegeofEngineeringandPhysicalSciences,UniversityofBirmingham,Edgbaston,Birmingham,B152TT,UK
E-mail:[email protected]
Inordertounderstandphoto-excitedprocessesithasbeenproventobeimportanttodescribesignificantquantumeffectssuchastunnellingandconicalintersections.Amethodofdirectquantumdynamicsforthestudyofsuchphoto-excitedprocesseshasrecentlybeenimplementedintheQuanticssoftwarepackage.TheDD-vMCG (directdynamicsby thevariationalmulti-configurationalGaussian)methodpromisestobefast,efficient,andwithbetterconvergencepropertiesthanpreviousmethodsbasedonclassicaltrajectories[1].Asitisinthedevelopmentphase,testingisrequired.TheunderlyingphysicalprocessesbywhichmutagenesisoccursinDNA/RNA,whetherbyUVradiationorspontaneous occurrence, has been the subject of extensive chemical and biological research.Prototypically the inter- and intra-molecular proton-transfers in excited states of 2-pyridone/2-hydroxypyridineandFormamide/Formamidicacidhavebeenusedasanaloguestothedescriptionofmutagenesis.Theypresentan interesting systemto studywith theDD-vMCGmethodas theymaydemonstratecompetitionbetweenproton-transferandnon-adiabaticcurvecrossing[2,3].Another photo-excited process of interest is the competition between charge-transfer and charge-migration.Anewdirectdynamicsmethod,basedontheEhrenfestapproach,hasbeenusedpreviouslytostudycharge-migrationintheToluenecation[4].AmodelHamiltonianfortheAllene(C3H4)radicalcationhasbeenusedasatestinpreviousQuanticsstudiesoncharge-transfer[5],andpresentsanidealsystemtotesttheEhrenfestapproach.[1]G.Richings,etal.,Int.Rev.Phys.Chem,.2015,34,269.[2]Q-S.Li,etal.,J.Phys.Chem.A,2005,109,3983.[3]L.Poisson,etal.,PCCP,2014,16,581[4]M.Vacher,elal.,J.Phys.Chem.A,2014,119,5165.[5]G.WorthandL.Cederbaum,Chem.Phys.Lett.,2001,348,477
25
TCGGraduateStudentMeeting
Aninvestigationintocompetitionbetweenhalogenbondingandhydrogenbondinginmicrosolvated1-methyl-5-halouracil
SimonW.L.HoganandTanjavanMourik
EaStCHEMSchoolofChemistry,UniversityofStAndrews,StAndrews,KY169ST,UK
E-mail:[email protected]
Aninvestigationintohalogenbondingandhydrogenbondinginteractionsbetweenamoleculeof1-methyl-5-halouracil(XU)(X=F,Cl,Br,I,orAt)andawatermolecule(XU-w)ortwowatermolecules(XU-2w),primarilyintheregionbetweentheC5-X5bondandtheC4=O4bondwasperformed[1].ForallcalculationstheM06-2Xfunctionalwasusedinconjunctionwitheitherthe6-31+G*basisset(forallelementslighterthaniodine)oraug-cc-pVDZ-PP(foriodineandastatine).ForXU-whalogenbondswerefoundtoformbetweenX5andthewateroxygenatom(Ow)whereXisBr,IorAt;whilethatinteractionwasfoundforX=Cl,Br,IorAtinthecaseofXU-2w.InthecaseofXU-2wthestructurewithahalogenbondalsoincludedwater-waterandwater-O4hydrogenbonds.ForXU-wallofthehalogenbondedminimawerefoundtobeconnectedtoahydrogenbondedminimumviaatransitionstate,andthegeometryandbarrierheightofeachtransitionstatewascomputed.Allminimaandtransitionstateswereconfirmedbyharmonicvibrationalfrequencyanalysis.Inallcasesthestrengthofthehalogenbond,thebarrierheightandlinearityoftheC5-X5-Owangleincreasesasthehalogengroupisdescended.Alloftheseobservationsareattributedtothegreaterpolarisability(andhencestrongersigmaholeeffect)asthehalogenbecomesheavier.ThelackofahalogenbondedClU-wdespiteitspresenceinthecaseofClU-2wisascribedtothestrongercompetingwater–O4hydrogenbond.ThepresenceofhalogenbondswithaC5-X5-Owangleintherange150°-160°degreesdemonstratestheflexibilityofthehalogenbondindepartingfromitsidealangle(linear)whentherearesecondaryfactorsbearingonthegeometryascanbefoundintherelativelycomplexchemicalenvironmentoftheXU-2wsystems.
Figure1:The1-methyl-5-halouracilpluswatersystem.X=F,Cl,Br,IorAt[1]S.W.L.HoganandT.vanMourik,J.Comput.Chem.,2016,37,763-770.
Xbondexample(AtXbond)
N3
C2
N1C6
C5
C4
X5
O4
Ow
Hw1
Hw2
26
Poster
PostersModellingtryptophantohemeelectrontransferandexcitationenergytransferinmyoglobin……….28ChristianSuess(UniversityofNottingham)TunnelingdynamicsofHF-H2Oonanaccurateanalyticpotential……….29ChuhuiXiao(UniversityofBristol)Anomalouspropertiesinnetworkmaterials……….30DomagojFijan(UniversityofOxford)AcomputationalstudyofGe5O(PO4)6……….31GregorMcInnes(UniversityofSt.Andrews)Gas-phaseandMgO(100)-supportedAu,Pd,andAuPdsub-nanometreclusters:Structuresandenergeticanalysis……….33HeiderA.Hussein(UniversityofBirmingham)Currentdensity-functionaltheoryusingmeta-generalizedgradientexchange-correlationfunctionals……….34JamesW.Furness(UniversityofNottingham)Structuresandenergylandscapesofmicro-hydratedClO3
-andClO4-
clusters……….35JohnC.Hey(UniversityofBirmingham)Cyclicbreakdownofringcurrentsusinggraphtheoreticalmethods……….36JosephClarke(UniversityofSheffield)Network-basedanalysisofmodelphotosyntheticsystems……….37LewisA.Baker(UniversityofWarwick)EffectofgraphenesupportonlargePtnanoparticles……….38LucasG.Verga(UniversityofSouthampton)Photo-excitedmoleculardynamicsofmoleculesassociatedwiththegreenfluorescentprotein……….39MarcusP.Taylor(UniversityofBirmingham)
27
Poster
Isotopeeffectcalculationsinthesupramolecularage……….40PhilippeB.Wilson(UniversityofBath)Aforcefieldfortheaccuratecalculationofthestructureandvibrationalspectroscopyofcarbonmaterials……….41PriteshTailor(UniversityofNottingham)AnewhybridfunctionalforDensityFunctionalTheoryinspiredbytheUnsoldapproximation……….42TimWiles(BristolUniversity)Vibrationalstructuresinthenear-UVelectroniccirculardichroismspectraofproteins……….43ZhuoLi(UniversityofNottingham)
28
Poster
Modellingtryptophantohemeelectrontransferandexcitationenergytransferinmyoglobin
ChristianSuess,NicholasA.BesleyandJonathanD.Hirst
SchoolofChemistry–UniversityofNottingham,UniversityPark,Nottingham,NG72RD,UK
E-mail:[email protected]
Electrontransfer(ET)isamongstthemostimportantchemicalprocesses,andareubiquitousthroughout nature. This has motivated the development of experimental techniques in order tocharacterisepathwaysof electron transfer andenergy transfer inproteins inmoredetail. Recently,Cherguiandco-workersusedtwo-dimensionalultraviolet(2D-UV)spectroscopytostudytheultrafastelectrontransferinmyoglobin[1].Myoglobinactsasanoxygencarrierinmuscletissueandcomprisesasinglepolypeptidechainof153aminoacidswithanironporphyrinactivesite.The2D-UVstudyfocusedontheETandexcitationenergytransfer(EET)betweenthetwotryptophanresidues(7Trpand14Trp)andtheheme.AshemeproteinsdonotfluoresceitisdifficulttodistinguishbetweenETorEEThencehowelectronsdecayremainsambiguous.Inthisposterwedescribethemodellingoftheseprocessesbaseduponquantumchemicalcalculations.Singleexcitationconfigurationinteraction(CIS)andtime-dependent density functional theory (TDDFT) are usedwithin the framework ofMarcus theory toestimatetheratesoftryptophantohemeETandEET.Keyintermediateresiduesbetweenthedonorandacceptorareidentifiedusingthepathwaystunnellingmodel,andtheinclusionoftheseresiduesiscriticalinTDDFTcalculationsoftheelectroncouplingmatrixelements.Strategiestoreducethecostofthecalculationssuchasusingarestrictedexcitationsubspacemethod[2]areexplored.Itisshownthat14Trpexcitationdecaysbyelectrontransfertothehemeonamuchfastertimescalethantheexcitationenergytransferprocesswhilst7Trprelaxesbyexcitationenergytransfertothehemefasterthantheelectrontransfer.
[1]C.Consani,G.Auböck,F.vanMourik,M.Chergui.Science,2016,339,1586-9.[2]Besley,N.A.ChemicalPhysicsLetters390,124-129.(2004)
29
Poster
TunnelingdynamicsofHF-H2Oonanaccurateanalyticpotential
ChuhuiXiaoandDavidP.Tew
SchoolofChemistry,UniversityofBristol,Bristol,BS81TH,UKE-mail:[email protected]
Thehydrogenbondis importantduetoitsdominantroleinnaturalscience.TheHF-H2O
complex, the simplest hydrogen halide-water complex, has received attention from bothexperimentalistsandtheoreticians[1].Experimentalspectra,however,arehardtoobtainbecauseofthelowvolatilityofwaterandhydrogenfluoridemixture[2]andhardtoassignduetothetunnelingdynamics[3].Abinitiocalculationofro-vibrationalenergylevelsonanaccurateelectronicpotentialcanprovide much needed insight.We built a potential energy surface (PES) by the least absoluteshrinkageandselectionoperator(LASSO)regressionandfitto10000CCSD(T)-(F12*)energiesatrandomgeometries [4]. LASSO regression is the state-of-the-art linear regression that canminimizeoverfittingbyconstrainedconditionswhenaddingamassivelyamountoffunctions.Thegeometriesand frequencies both attheequilibriumandtransitionstateobtained fromPESagreecloselywiththeabinitioresults.Additionally,thebarriertoinversionis126.55cm-1 forabinitiocalculationand132.39cm-1forPES,bothofwhichareclosetotheexperimentaldata,126cm-
1[5].Theconvergedtunnelingenergylevelsarealsoobtainedusingfull-dimensionalvibrationalapproach–VSCFandVCI,usingtheReactionPathHamiltonian[6].
Figure1.StructuresofHF-H2Ocomplex.(1)FH-OH2withCssymmetry, (2)FH-OH2withC2vsymmetry[1]V.P.Bulychev,E.I.Gromova,andK.G.Tokhadze,Opt.Spectrosc+.,2004,96,774-788.[2]R.K.Thomas,Proc.R.Soc.A.,1975,344,579-592.[3]S.P.Belov,V.M.Demkin,N.F.Zobov,E.N.Karyakin,A.F.Krupnov,andI.N.Kozin,J.Mol.Spectrosc.,2007,241,124-135.[4]WataruMizukami,ScottHabershon,andDavidP.Tew,J.ChemPhys.,2014,141,144310-144319.[5]A.C.LegonandD.J.Millen,FaradayDiscussChem.Soc.,1982,73,71-87.[6]W.H.Miller,N.C.Handy,andJ.E.Adams,J.Chem.Phys.,1980,72,99-112.
30
Poster
Anomalouspropertiesinnetworkmaterials
DomagojFijanandMarkWilson
DepartmentofChemistry,PhysicalandTheoreticalChemistryLaboratory,UniversityofOxford,SouthParksRoad,OxfordOX13QZ,UnitedKingdom
E-mail:[email protected];[email protected]
Thermodynamic and kinetic anomalies are often encountered in tetrahedral liquids, mostfamously inwater(forexample,thedensityanomaly).Theoriginoftheanomalies isoftenlinkedtobehaviour of quantities associated to phase transition phenomena which occur in the metastablesupercooledregimethatislargelyinaccessiblebyconventionalexperiments.Asaresultsimulationsareoften used to explore this problem. Several theories and scenarios have been proposed that linkbehaviourofanomalouspropertiestotheexistenceofaliquid-liquidcriticalpoint[1][2][3].Stillinger-Weber(SW)potentialsareoftenemployedtomodeltetrahedralliquids.Thesepotentialsarecomposedofastandardpairwisetermwithexponentialdecayandatriplettermwhichpenalizesdeviationsfromidealtetrahedralangles[4].InrecentyearsthecriticalpointforSWsiliconhasbeenuncovered[5]andlociofanomalouspropertiescalculatedforconstantpressurefordifferentstrengthsoftripletterminSWpotential[6].However,nosystematicstudyoftheSWpotentialthatinvolvesthecalculationofcriticalpointsandspinodallinesandlinksthemtoanomalouspropertiesasafunctionofthestrengthoftriplettermhasyetbeenreported.InthisstudywetakeasystematicapproachtoexploretheparameterspaceofthetriplettermintheSWpotentialatvarioustemperatures,pressuresanddensities.Thisenablesustomorethoroughlyunderstandtheappearanceofthermodynamicandkineticanomaliesintetrahedralliquidsandtheirconnectiontotheunderlyingtetrahedralityofthesystem.
[1]R.J.Speedy,JournalofPhysicalChemistry,1982,86(6),982–991.[2]S.Sastry,P.G.Debenedetti,F.SciortinoandH.E.Stanley,Phys.Rev.E1996,53(6),6144–6154.[3]P.H.Poole,F.Sciortino,U.EssmannandH.E.Stanley,Nature,1992,360(6402),324–328.[4]F.H.StillingerandT.Weber,Phys.Rev.B,1985,31(8),5262–5271.[5]V.V.Vasisht,S.SawandS.Sastry,NaturePhysics,2011,7(7),549–553.[6]W.Hujo,B.S.Jabes,V.K.Rana,C.ChakravartyandV.Molinero,JournalofStatisticalPhysics,2011,145,293–312.
31
Poster
AcomputationalstudyofGe5O(PO4)6
GregorMcInnes,MarkTham,JohnIrvineandHerbertFrüchtl
Eastchem,SchoolofChemistry,UniversityofSt.Andrews,NorthHaugh,St.Andrews,KY169ST,UKE-mail:[email protected]
SolidOxideFuelCells(SOFCs)arebeinginvestigatedforuseaspossiblegreenenergystorage
devices.ThiscomputationalstudyisbasedonpracticalworkconductedonGe5O(PO4)6whichisbeingconsideredforuseasapossibleelectrolytematerialandattemptstofindthemigrationpathwaythoughthestructureusedbyoxygen.ThecrystalstructureofGe5O(PO4)6consistsofGeO6octahedraandGeO4tetrahedralinkedbyPO4groupsforminga3dimensionallattice.
Figure1.ProjectionofGe5O(PO4)6wherea)istheunitcellshowingtheatomscrystallograpicallydefinedasGe1 (purple), Ge2 (Green),Ge3 (light blue) and phosphorus (grey). b) shows the oxygen atomscrystallographicallydefinedasO1(red),O2(yellow),O3(black),O4(pink)andO5(purple)Practicalworkhasshownthatthismaterialhasaconductivityofof1.1x10-4Scm-1forbulkprocesses.Thiscorrespondstoanactivationenergyof0.35eVfortheoxygenmigrationprocess.Thisactivation
32
Poster
energyinconjunctionwithresultsappearingtoshowthatO1(showninfigure1)ismobile,hasresultedintheproposalthatoxygenmigrationoccursalongthec-axisofthelatticeinvolvingthemovementoftheO1oxygenalongthelatticeinaninterstitialcymechanism.Thiscomputationalstudylooksatpossiblepathwaysthroughthelatticeinanattempttofindoutiftheproposedpathwayiscorrect,andifnot,thenattempttofindapathwaywhichfitswiththeobservedexperimental results.Wehave so farusedNudgedElasticBand calculations to investigatedifferentvacancymechanisms throughthe lattice.The lowestenergypathwaywehave foundso farusingavacancyorinterstitialcymechanismoccursthroughthea/b-axisandwithanactivationbarrierof2eV,withmovementalongthec-axisshowingamuchhigherbarrier,sothatthelattercanberuledout.Theenergydifferencebetweenthelowestenergypathwayandtheexperimentalresultsleadsustoconcludethatyetanotherpathwaymustbepresent.Morepathwaysarenowbeinginvestigatedwithafocusonpathways involving an alternative lattice structure that has been shown to be present within theGe5O(PO4)6electrolyte(showninfigure2)
Figure2.ApossiblealternativelatticestructureforGe5O(PO4)6
33
Poster
Gas-phaseandMgO(100)-supportedAu,Pd,andAuPdsub-nanometreclusters:structuresandenergeticanalysis
HeiderA.Hussein,1,2RoyL.Johnston1
1SchoolofChemistry,UniversityofBirmingham,Birmingham,UnitedKingdom2DepartmentofChemistry,CollegeofScience,UniversityofKufa,Najaf,Iraq
E-mail:[email protected]
Sub-nanometreclusterscanbedefinedasgroupsoraggregatesofafewtotensofmetalatomswhicharebelow1.0nminsize.Theseclustersmaycontainthesameatoms,givingpureclusters,ortwoormoredifferentatomspresentinghetero-clusters. Inthisproject,TheBirminghamParallelGeneticAlgorithm(BPGA)hasbeenadoptedfortheglobaloptimizationoffreeandMgO(100)-supportedPd,AuandAuPdnanoclusterstructures,overthesizerange4-10atoms.Structureswereevaluateddirectlyusingdensityfunctionaltheory,whichhasallowedtheidentificationofPd,AuandAuPdglobalminima.Theenergetics,structures,andtendencytowardssegregationhasbeenevaluatedusingdifferentstabilitycriteria suchasbindingenergy,excessenergies,andseconddifference inenergy.Theabilityof thesearchestofindtheputativeglobalminimumhasbeenassessedusingahomotopsearchmethod,whichshowsahighdegreeofsuccess.
34
Poster
Currentdensity-functionaltheoryusingmeta-generalizedgradientexchange-correlationfunctionals
JamesW.Furness1,JoachimVerbeke1,AndrewM.Teale1,ErikI.Tellgren2,Stella
Stopkowicz2,UlfEkström2andTrygveHelgaker2
1SchoolofChemistry,UniversityofNottingham,Nottingham,UK
2CentreforTheoreticalComputationalChemistry,UniversityofOslo,Oslo,NorwayE-mail:[email protected];[email protected]
Wepresenttheself-consistentimplementationofcurrent-dependent(hybrid)metageneralized
gradientapproximation(mGGA)densityfunctionalsusingLondonatomicorbitals.Apreviouslyproposedgeneralizedkineticenergydensity[1,2]arisingnaturallyfromconsiderationofthesphericallyaveragedexchangehole[3], is utilized to implementmGGAs in the frameworkof Kohn-Shamcurrentdensityfunctional theory (KS-CDFT). A unique feature of the non-perturbative implementation of thesefunctionalsistheabilitytoseamlesslyexploreawiderangeofmagneticfieldsupto1a.u.(~235000T)instrength.CDFTfunctionalsbasedontheTPSS[4]andB98[5]formsareinvestigatedandtheirperformanceisassessedbycomparisonwithaccurateCCSD(T)data[6].IntheweakfieldregimemagneticpropertiessuchasmagnetizabilitiesandNMRshieldingconstantsshowmodestbutsystematicimprovementsoverGGAfunctionals.However,instrongfieldregimethemGGAbasedformsleadtoasignificantlyimproveddescriptionoftherecentlyproposedperpendicularparamagneticbondingmechanism[7],comparingwellwithCCSD(T)data[8].Incontrasttofunctionalsbasedonthevorticity[9]theseformsarefoundtobenumericallystable[10]andtheiraccuracyathighfieldsuggeststheextensionofmGGAstoCDFTviathegeneralizedkineticenergydensityshouldprovideausefulstartingpointforfurtherdevelopmentofCDFTapproximations[11].[1]A.D.Becke,Can.J.Chem.74,995(1996)[2]J.Tao,Phys.Rev.B.71,205107,(2005)[3]J.F.Dobson,J.Chem.Phys.98,8870(1993)[4]J.Tao,J.Perdew,V.StaroverovandG.E.Scuseria,Phys.Rev.Lett.91,146401(2003)[5]A.D.Becke,J.Chem.Phys.109,2092(1998)[6]A.M.Teale,O.B.Lutn_s,T.Helgaker,D.J.Tozer,J.Gauss,J.Chem.Phys.138,024111(2013)[7]K.K.Lange,E.I.Tellgren,M.R.Ho_mann,T.Helgaker,Science337,327(2012).[8]S.Stopkowicz,K.K.Lange,E.I.TellgrenandT.Helgaker,arXiv:1505.08045v1,(2015)[9]G.VignaleandM.Rasolt,Phys.Rev.B.37,10685(1988)[10]E.Tellgren,A.M.Teale,J.W.Furness,K.K.Lange,U.Ekstr�omandT.Helgaker,J.Chem.Phys.140,034101(2014)[11]J.W.Furness,J.Verbeke,E.I.Tellgren,S.Stopkowicz,U.Ekstrm,T.Helgaker,A.M.Teale,arXiv:1505.07989,(2015)
35
Poster
Structuresandenergylandscapesofmicro-hydratedClO3-and
ClO4-clusters
JohnC.Hey,EmilyJ.DoyleandRoyL.Johnston
SchoolofChemistry,UniversityofBirmingham,Birmingham,B152TT,UK
E-mail:[email protected]
Electrolyticsolutionsareextremelyimportantinbothbiologyandindustry,asthepropertiesofsolutionscanbedrasticallyalteredbythepresenceofsalts.1Saltshavelongbeenknowntoaffectthesolubilityandstabilityofproteinsinsolution,in1888,HofmeisterandLewithdevisedanorderingforseveralcommonions,rankingthemaccordingtothiseffect,thisorderingisknownastheHofmeisterseries.2–5Perchlorate(𝐶𝑙𝑂%&)andChlorate(𝐶𝑙𝑂%&)arebothhighlychaotropicHofmeisterions,inthattheypromotedisorderwithinthehydrogenbondingnetworkandreducethesolubilityofproteins.6,7Sulfate(𝑆𝑂%)&)ontheotherhandisakosmotropicHofmeisterion,whichincreasesproteinstabilityandpromotesorderwithinthehydrogenbondingframeworkofwater.8–11Inthisworkwefindlowenergyconformationsformicro-hydratedperchlorateandchlorateclusterswith𝑁+,- ≤ 12watersandpresentputativeglobalminima.Theselowenergyconformationswerefoundusingabasin-hoppingsearchwithempiricalpotentialsforthehalo-oxyanionandtheTIP4Ppotentialforwater,usingthepelesoftwarepackageontheBlueBEARHPCcluster.ThesestructureswerethenlocallyminimisedattheDFTlevelusingtheB3LYPexchange-correlationfunctionalandthe6-311++G**basisset.6,12–16 Theenergy landscapesof the chlorateandperchlorate clusters are thenexploredusingadoubly-nudgedelasticbandmethodandvisualisedasdisconnectivitytreesbeforebeingcomparedtooneanotherandtoSulfatetogiveacomparisonoftwodifferentchaotropeswithastronglykosmotropicion.17[1]A.P.dosSantosandY.Levin,FaradayDiscuss.,2013,160,75–87[2]W.J.XieandY.Q.Gao,J.Phys.Chem.Lett.,2013,4,4247–4252[3]M.T.Record,E.Guinn,L.PegramandM.Capp,FaradayDiscuss.,2013,160,9–44[4]M.G.Cacace,E.M.LandauandJ.J.Ramsden,Q.Rev.Biophys.,1997,30,241–277[5]W.Kunz,Curr.Opin.ColloidInterfaceSci.,2010,15,34–39[6]M.D.Baer,I.-F.W.Kuo,H.BluhmandS.Ghosal,J.Phys.Chem.B,2009,113,15843–15850[7]G.M.BrownandB.Gu,Thechemistryofperchlorateintheenvironment,Springer,2006[8]L.C.Smeeton,J.D.Farrell,M.T.Oakley,D.J.WalesandR.L.Johnston,J.Chem.TheoryComput.,2015,11,2377–2384[9]N.Mardirossian,D.S.Lambrecht,L.McCaslin,S.S.XantheasandM.Head-Gordon,J.Chem.TheoryComput.,2013,9,1368–1380[10]D.S.Lambrecht,G.N.I.Clark,T.Head-GordonandM.Head-Gordon,J.Phys.Chem.A,2011,115,11438–54[11]J.T.Obrien,J.S.Prell,M.F.BushandE.R.Williams,J.Am.Chem.Soc.,2010,132,8248–8249[12]Pythonenergylandscapeexplorer:http://pele-python.github.io/pele/Accessedon:03/12/2015.[13]D.J.WalesandJ.Doye,J.Phys.Chem.A,1997,93,5111–5116[14]D.J.WalesandH.A.Scheraga,Science(80-.).,1999,285,1368–1372[15]S.KazachenkoandA.J.Thakkar,Chem.Phys.Lett.,2009,476,120–124[16]D.J.WalesandM.P.Hodges,Chem.Phys.Lett.,1998,286,65–72[17]S.A.TrygubenkoandD.J.Wales,J.Chem.Phys.,2004,120,2082–2094
36
Poster
Cyclicbreakdownofringcurrentsusinggraphtheoreticalmethods
JosephClarkeandPatrickFowler
DepartmentofChemistry,UniversityofSheffield,SheffieldS37HF,UKE-mail:[email protected]
The graph theoretical model of conjugated-circuit methods1 gives a qualitatively correct
calculationoftheringcurrentsofbenzenoids.Themodelcanbeapproximatelycomparedwiththe‘goldstandard’ofHückel-London2andfullabinitiocalculations.3However,conjugated-circuitmodelshavefundamental flaws when applied to some simple systems, such as cyclopentadiene. Furthermore,conjugated-circuitmodelsgiveverysimpleinterpretationsforisland-likesystems,suchasperylene,butmaybetoosimpleforextensions.Wedescribeacycle-decompositionoftheHückelmethodthatgivesanalysisof cyclecontributions tocurrentandshouldallowcalibrationofnewconjugatedcircuit-likemodelsofringcurrentsthatapplymuchmorewidelythanthepresentKekuléan-onlymodels.[1](a)Randić,M.,Chem.Phys.Lett.,2010,500,123-127.(b)Mandado,M.,JournalofChemicalTheoryandComputation,2009,5,2694-2701andSupplementaryInformation.(c)Ciesielski,A.;Krygowski,T.M.;Cyranski,M.K.;Dobrowolski,M.A.;Aihara,J.-i.,PCCP,2009,11,11447-11455.(d)Fowler,P.W.;Myrvold,W.,TheJournalofPhysicalChemistryA,2011,115,13191-13200[2](a)London,F.,J.Phys.Radium,1937,8,397-409.(b)McWeeny,R.,Mol.Phys.,1958,1,311.(c)Pople,J.A.,Mol.Phys.,1958,1,175[3]Steiner,E.;Fowler,P.W.,J.Phys.Chem.A,2001,105,9553-9562
37
Poster
Network-basedanalysisofmodelphotosyntheticsystems
LewisA.BakerandScottHabershon
DepartmentofChemistryandCentreforScientificComputing,UniversityofWarwick,Coventry,UK.E-mail:[email protected]
Pigment-proteincomplexes(PPCs)playacentralrole infacilitatingexcitationenergytransfer
(EET) from light-harvesting antenna complexes to reaction centres in photosynthetic systems;understandingmolecularorganisationinthesebiologicalnetworksiskeytodevelopingbetterartificiallightharvestingsystems.Wecombinequantum-mechanicalsimulationsandanetwork-basedpictureoftransporttoinvestigatehowchromophoreorganisationandproteinenvironmentinPPCsimpactsonEETefficiencyandrobustness[1-3].FocusingontheFenna-Matthews-Olson(FMO)complexandthelightharvestingcomplex(LHCII),weconsidertheimpactonEETefficiencyofbothdisruptingthechromophorenetworkandchangingtheinfluenceof(localandglobal)environmentaldephasing.Surprisingly,wefinda large degree of resilience to changes in both chromophore network and protein environmentaldephasing,theextentofwhichisgreaterthanpreviouslyobserved;forexample,FMOandLHCIImaintainEETwhen50%oftheconstituentchromophoresareremoved.Overall,theserobustnessandefficiencycharacteristics areattributed to thehighly connectednatureof the chromophorenetworkand thepresenceofmultipleEETpathways,featureswhichmighteasilybebuilt intoartificialphotosyntheticsystems.
Figure1.Modelreductionoftheenergytransportpathwayingreensulphurbacterium.[1]A.EisfieldandJ.Briggs,Phys.Rev.E,2012,85,046118.[2]J.Moix,J.Wu,P.Huo,D.Coker,andJ.Cao,J.Phys.Chem.Lett.,2011,2,3045.[3]L.BakerandS.Habershon,J.Chem.Phys.,2015,143,105101.
38
Poster
EffectofgraphenesupportonlargePtnanoparticles
LucasG.Verga,AndreaRussell,Chris-KritonSkylaris
DepartmentofChemistry,UniversityofSouthampton,UniversityRoad,Southampton,SO171BJ,UKE-mail:[email protected]
Duringthelastdecades,theinterestinmorepowerfulandflexiblewaystogenerateenergy,such
asthefuelcelltechnology,isconstantlyincreasing.Fuelcellsarecapableofproducingelectricalenergywithhigherefficiencyandautonomyandmayhelptoreducethedependenceonfossilfuelsandlowertheemissionoftoxicproductsintotheatmosphere.Specifically,thedirectmethanolandethanolfuelcells,DMFCsandDEFCS,areemergingtechnologieswithseveralpossibleapplicationsduetotheeasinessofhandlingthesefuels,theirhighenergydensity,lowpollutantemission,andlowworkingtemperatures.OneofthemainchallengesonDEFCsisthesearchforefficientcatalystsfortheethanoloxidationreaction,EOR[1],andtheoxygenreductionreaction,ORR[1].Nowadays,state-of-the-artcatalystsarecreatedviadepositionofmonolayersornanoparticlesofthecatalyticmaterialoversupports,increasingtheactivesurfaceareaanddecreasingtheloadingofcatalyticmaterialand,consequently,theoverallcostoffuelcells[1]–[3].Therefore,theunderstandingabouttheinteractionbetweencatalystandsupportcanbeessentialtodesigningefficientDEFCscatalysts.Here,weemploylarge-scaleDFTsimulationsformetallicsystems[4]asimplementedintheONETEPlinear-scalingDFTprogram[5]tostudyplatinumclustersinteractingwithasinglelayergraphene.Wecomparethestabilityofplatinummonolayersandnanoparticlesinteractingwiththesupport,andanalyseitsoptimisedgeometriesandelectronicproperties.Ourresultsshowthatnanoparticlesaremorestablethanmonolayers, and that the difference between their stabilities increases with the system size.Moreover, our optimized platinum structures exhibit inter-atomic expansion in facets close to thegraphenesheet,andtheelectronicanalysisshowselectrontransferfromtheplatinumclusterstothesupport.BotheffectscanchangethecatalyticbehaviourofthePtnanoparticles,showingtheimportanceofdeeperunderstandingofthesupporteffects.[1]J.FriedlandU.Stimming,ElectrochimicaActa.,2013,101,41.[2]M.Shao,Q.Chang,J.-P.Dodelet,andR.Chenitz,Chem.Rev.,2016,116,3594.[3]S.Navalon,A.Dhakshinamoorthy,M.Alvaro,andH.Garcia,Coord.Chem.Rev.,2016,312,99.[4]Á.Ruiz-SerranoandC.-K.Skylaris,J.Chem.Phys.,2013,139,054107.[5]C.-K.Skylaris,P.D.Haynes,A.A.Mostofi,andM.C.Payne,J.Chem.Phys.,2005,122,084119.
39
Poster
Photo-excitedmoleculardynamicsofmoleculesassociatedwiththegreenfluorescentprotein
MarcusP.TaylorandGrahamA.Worth
SchoolofChemistry,UniversityofBirmingham,Edgbaston,Birmingham,B152TT
E-mail:[email protected]
Therehasbeenimmenseinterestinthegreenfluorescentprotein(GFP)duetoit'splethoraofpotentialapplicationsand,asyet,lackoffulldetailsurroundingitsphotophysics.[1,2]Inparticularit'sbroadphotoelectronspectrumandrelativelocationoftheelectronicstatesfortheanionandradicalformhaveattractedsignificantresearchbothexperimentallyandtheoretically.[3-6]Oneapproachtotacklethisproblemisabottom-upapproach,startingwithanalysisofthecomponentscomprisingtheGFPchromophore;hydroxybenzylidene-2,3-dimethylimidazolinone(HBDI).Photodetachmentspectrahavebeen obtained for the anion to radical transition of imidazole, bis-imidazoloxy, phenoxide andbisphenoxide. The spectra were calculated from wavepacket propagation using the QUANTICSprogram[7,8],apre-requisiteofwhich is thegenerationofa two-statemodelHamiltonian foreachmolecule.ConstructionoftheseHamiltoniansrequiredthefittingofparameterstopointscalculatedalongthepotentialenergysurfaceusingabinitiomethods.
[1]J.J.vanThor,Chem.Soc.Rev.,2009,38,2935-50.[2]P.J.TongeandS.R.Meech,J.Photochem.Photobiol.AChem.,2009,205,1-11.[3]D.A.HorkeandJ.R.R.Verlet,Phys.Chem.ChemPhys.,2012,14,8511-8515.[4]C.R.S.Mooney,H.H.Fielding,etal.,J.ChemPhys.A,2012,116,7943-7949.[5]Y.Toker,L.H.Anderson,etal.,Phys.Rev.Lett.,2012,109,128101-4.[6]K.B.BravayaandA.I.Krylov,J.Phys.Chem.A.,2013,117,11815-22.[7]G.A.Worth,K.Giri,G.W.Richings,M.H.Beck,A.JäckleandH.-D.Meyer.TheQUANTICSPackage,Version1.1,(2015)[8]M.H.Beck,A.Jäckle,G.A.WorthandH.-D.Meyer.,Phys.Rep.,2000,324,1-105.
40
Poster
Isotopeeffectcalculationsinthesupramolecularage
PhilippeB.WilsonandProf.IanH.Williams
DepartmentofChemistry,UniversityofBath,ClavertonDown,Bath,BA27AY,UKE-mail:[email protected]
Kinetic isotopeeffectsarewidelyusedasexperimentalprobesofchemicalandbiochemical
reactionmechanisms,buthowtheyshouldbeinterpretedforenzymicreactionsremainsproblematic.ComputationalsimulationusingQM/MMmethodsiscapableofprovidingvaluableinsight,butrobustprocedures have not yet been established, and opinion still differs between experimental(1,2) andcomputational(3,4)approachestoenzyme-catalyzedmethyltransfer.Ourrecentstudieshaveindicatedthattheelectrostaticenvironmentaroundasiteofisotopicsubstitutionmayhaveasignificantinfluencethathasnotpreviouslybeentakenintoaccountintheinterpretationofexperimentalkineticisotopeeffects.Wehaveshownthatisotopeeffectsfortransferofamethylcationfromvacuumtoadielectriccontinuumvarydramaticallyovertherangeofdielectricconstantsnormallyassociatedwithenzymeactivesites,(5)andhavearguedthatthecorrectionsforvibrationalanharmonicityonisotopeeffectsarebesttreatedbymeansofscalingofcalculatedharmonicfrequencies.(6)Wehavealsoshownthathydrogen-bondinginteractionsbetweenmethylCHbondsandoxygenatomswithinacage environmentmayhave a significant influenceupon kinetic isotope effects formethyl transferbetweenanucleophileandnucleofuge.Thismayimplyanalternativeexplanation,atleastinpart,forobservedtrendsinkineticisotopeeffectsforenzyme-catalysedmethyltransfer.(1,2).Wesuggestthatourmethodology is applied for the calculationand interpretationof isotopeeffects, anddetail possiblealternativesandapproximationsforfutureworkinthefield.[1]J.ZhangandJ.P.Klinman,JournaloftheAmericanChemicalSociety,2011,133,17134-17137[2]J.Zhang,H.J.Kulik,T.J.MartinezandJ.P.Klinman,ProceedingsoftheNationalAcademyofSciencesoftheUnitedStatesofAmerica,2015,112,7954-7959[3]J.JavierRuizPernia,G.D.RuggieroandI.H.Williams,J.Phys.Org.Chem.,2013,26,1058-1065[4]N.Kanaan,J.J.R.PerniaandI.H.Williams,ChemicalCommunications,2008,DOI:10.1039/b814212b,6114-6116[5]P.B.Wilson,P.J.Weaver,I.R.GreigandI.H.Williams,JournalofPhysicalChemistryB,2015,119,802-809[6]P.B.WilsonandI.H.Williams,MolecularPhysics,2015,113,1704-1711[7]P.B.WilsonandI.H.Williams,AngewChemIntEdit,2016,55,3192-3195.
41
Poster
Aforcefieldfortheaccuratecalculationofthestructureandvibrationalspectroscopyofcarbonmaterials
PriteshTailor,RichardJ.WheatleyandNicholasA.Besley
SchoolofChemistry,UniversityofNottingham,Nottingham,NG72RD
Email:[email protected]
Theaccuratepredictionofthevibrationalspectroscopyofcarbonnanomaterialsisaproblemoffundamental interest and a challenge for computational methods. The capability to compute thevibrational frequencies and associated spectra of these systems accurately can potentially aid theinterpretation and classification of carbon nanotubes (CNT) and graphene in experimentalmeasurementsandallowtherelationshipbetweenthemolecularstructureandtheobservedfeaturestobeexplored.Calculationofthevibrationalspectroscopyofthesematerialsusingquantumchemistrywithinanon-periodic framework is computationally too expensive. An alternative approach is to simplify thedescriptionoftheforce-fieldthroughtheuseofanempiricalpotential.Forsuchmethodstobeofvaluethentheresultingdecreaseincomputationalcostcannotleadtoanunacceptablereductioninaccuracy.HerewepresentafullyempiricalmethodformodelingtheRamanspectroscopyofCNTsandgraphene.The calculations use a purpose built force-field based on the Murrell-Mottram potential [1] incombinationwiththeEmpiricalBondPolarizabilitymodel.AnalyticalfirstandsecondderivativesoftheMurrell-MottramhavebeenimplementedandthepotentialreparameterizedviaaMonte-Carlo“hessianmatching” approach creating a force-field which accurately models the vibrational behavior andspectroscopy of CNTs and graphene. It is shown that the potential accurately models the Ramanspectroscopyofthesesystemsatafractionofthecomputationalcostallowingfortheaccurateatomisticvibrationalanalysisofsystemswithgreaterthan10,000atoms.Subsequently,theRamanspectroscopyofCNTswithdefectsisexplored.
[1]J.N.MurrellandR.E.Mottram,Mol.Phys.,1990,69,571–585.
42
Poster
AnewhybridfunctionalforDensityFunctionalTheoryinspiredbytheUnsoldapproximation
TimWilesandFredManby
BristolUniversitySchoolofChemistry,England
E-mail:[email protected]
DensityFunctionalTheory(DFT)isasuccessfulab-initiomethodforcalculatingtheelectronicstructureofmolecules.Itssuccessisduetoitslowscalingincomputationalcomplexitywithsystemsize.Theenergyofthemolecule isexpressedasafunctionalof𝜌23 𝐫 , thedensityofthe”Kohn-Shamauxiliarysystem”ateverypointinspace.”Hybrid”functionalsareawidely-usedcorrectionthatcanbeaddedtotheDFTenergytoimproveitsaccuracy.Thesefunctionalsdependonthesingle-particlereduced-densitymatrix𝜌23 𝐫, 𝐫′ ,inadditiontothedensity𝜌23 𝐫 .Wepresentanewhybridfunctionalinspiredbythe”Unsoldapproximation”[1].WeaimtotestthisnewmethodagainstCoupled-ClusterTheorycalculationsoftheelectronicenergyofmolecules.
[1]A.Unsold,Z.Phys.,1927,43,563.
43
Poster
Vibrationalstructuresinthenear-UVelectroniccirculardichroismspectraofproteins
ZhuoLiandJonathanD.Hirst
SchoolofChemistry,UniversityofNottingham,UniversityPark,NottinghamNG72RD,UnitedKingdom
E-mail:[email protected]
A fully quantitative theory of the relationship between protein conformation and opticalspectroscopywouldfacilitatedeeperinterpretationandinsightsintobiophysicalandsimulationstudiesofproteindynamicsandfolding.Weemploythestate-averagedCASSCFmethodtocalculatevibrationalstructuresoftoluene,p-cresoland3-methylindole,whichrepresentthechromophoresinthearomaticaminoacidsphenylalanine,tyrosineandtryptophan,respectively.TheresultsofthesecalculationsareusedtoincorporatetheFranck-Condoneffectsintomatrixmethodcalculationsoftheelectroniccirculardichroism(CD)spectraofproteins inthenear-ultraviolet.Asetof40proteins,whosestructuresarereportedintheproteindatabank,arecalculatedtoassesstheinfluenceofvibrationalstructuresintheaccuracyofcalculations.Mutantsofvariousproteinsarecalculatedtoillustratetherelationshipbetweenspectrachangesandthestructuraldifferencesinducedbythemutation.ComputedspectraofsomeselectedproteinsfromthedatasetarecomparedwiththecalculationsconsideringtheconformationaldiversitybasedontheavailabilityoftheNMR-determinedproteinstructures.OurcalculationsconsideringvibrationalstructuresofthearomaticchromophoreshaveprovidedsomefurtherinsightintothephysicaloriginsofthenatureofproteinCDspectrainthenear-UV.