Download - Nanotech2010 High Throughput
Materials discovery with ab initio high throughput calculations
G. Fitzgerald, G. Goldbeck
A. Perlov, Accelrys Software Inc
M. Sarwar, S. French, S. Garçia, A. MartinezM. Sarwar, S. French, S. Garçia, A. Martinez
D. Thompsett, Johnson Matthey
TechConnect WORLD Conference, June 2010, Anaheim, CA
Materials discovery with ab initio high throughput calculations
G. Fitzgerald, G. Goldbeck-Wood, J.L. Gavartin,
A. Perlov, Accelrys Software Inc
M. Sarwar, S. French, S. Garçia, A. Martinez-Bonastre, M. Sarwar, S. French, S. Garçia, A. Martinez-Bonastre,
D. Thompsett, Johnson Matthey
TechConnect WORLD Conference, June 2010, Anaheim, CA
Statement
• Materials discovery typically involves exploration of very large phase space.
• Quantum and atomistic simulation technology are
sufficiently mature to be used to screen materials and
come up with lead candidates.
Bulk and surface defects Alloying
Defect decoration Surface segregation
© 2009 Accelrys, Inc.
come up with lead candidates.
• Robust, yet flexible software infrastructures make it feasible to
– Screen materials even with compute-heavy simulation methods.
– Provide a knowledge and decision base for research teams.
Materials Studio
Materials discovery typically involves exploration of very large phase space.
Quantum and atomistic simulation technology are
sufficiently mature to be used to screen materials and
Clustering
Skin formation
2
Robust, yet flexible software infrastructures make it feasible to
heavy simulation methods.
Provide a knowledge and decision base for research teams.
Pipeline Pilot Client
Pipeline Pilot
Web Port
Materials Studio Collection
Fuel Cell Catalyst application
• Market problem: Fuel Cells issues include
– High Cost
– Limited stability
• Technology problems
– Catalytic breakdown of O2 is rate determining
– Catalysis relies on Platinum
– other metals do not to perform well enough.
• R&D problems: Finding alternatives to Pt
– Different alloy combinations
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– Different alloy combinations
– Different alloy microstructures
– i.e. Screening thousands of materials
• Modeling problem: High throughput & relevance
– Complex enumeration of periodic structures
– Long calculation times
– Property analysis relevant to experiment
is rate determining
other metals do not to perform well enough.
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Modeling problem: High throughput & relevance
Complex enumeration of periodic structures
Overall:½O2+H2 �
PEM Fuel Cells
© 2009 Accelrys, Inc.
Anode- hydrogen oxidation:
H2 2H+ + 2e-
� H2O+ electricity
4
Cathode- oxygen reduction:
½O2 +2H+ + 2e- H2O
1
1.2
1.4
Cell Potential [V]
Theoretical Cell Voltage [E° = 1.23 V]
Theoretical cell voltage: 1.23V
Actual much less due to various loss processes
Voltage losses in a PEMFC
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0
0.2
0.4
0.6
0.8
0 200 400 600 800
Current Density [mA/cm2]
Cell Potential [V]
Cathode Activation
Theoretical Cell Voltage [E° = 1.23 V]
Actual much less due to various loss processes
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1000 1200 1400
Current Density [mA/cm2]
Cell Resistance
Anode Activation
Mass Transport
Cell Performance
Adsorption of O2 Dissociation of O
Dissociative ORR mechanism in PEMFC
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e-
Combination with a second proton +e
….to form OH
e-
Dissociation of O2 Combination with a proton +e-….
Dissociative ORR mechanism in PEMFC
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Combination with a second proton +e-….
….to form H2O
Ideal Catalyst – Sabatier’s Principle
• The optimum catalyst-adsorbate interaction must
– Not be too weak:
• Chemical bonds between surface and adsorbate can be formed
• Internal bonds weakened so intermediates can be generated
– Not be too strong
• Intermediates generated can react further
• Desorbtion takes place and freeing up of adsorption sites
• Pt is close to optimum, but expensive
© 2009 Accelrys, Inc.
Catalytic
Activity
• Pt is close to optimum, but expensive
– Other pure metals perform worse
– What about alloys?
Sabatier’s Principle
adsorbate interaction must
Chemical bonds between surface and adsorbate can be formed
Internal bonds weakened so intermediates can be generated
Intermediates generated can react further
Desorbtion takes place and freeing up of adsorption sites
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Metal-adsorbate bond strength
Pt
Phase Space
Activity
© 2009 Accelrys, Inc.
With high throughput modeling,that would otherwise not be covered
0% - Pt 50% - Pt100% - Co 50% - Co
Phase Space
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modeling, phase space to be exploredcovered experimentally.
100% - Pt0% - Co
Sampling must include structure and composition
Bulk and surface defects Alloying
© 2009 Accelrys, Inc.
Defect decoration Surface segregation
Sampling must include structure and composition
Alloying Clustering
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Surface segregation Skin formation
…
Overview of approach
• Objective: find alloy with similar profile as Pt, slightly weaker bonding
• Generate representative catalyst surface models
• Calculate key properties and determine descriptors of ORR
activity and bonding:
– Material Stability (Segregation Energies)
© 2009 Accelrys, Inc.
– Material Stability (Segregation Energies)
– O adsorption Energies
– OH adsorption Energies
– d-band centres
– electronic workfunction
– thermodynamics of reaction steps
• Methodology:
– Plane Wave Density Functional Theory – CASTEP
– High throughput strategies, automation
– Data accumulation and storage in database
– Data Management and reporting
Catalytic
Activity
Metal-adsorbate bond strength
Ptfind alloy with similar profile as Pt, slightly weaker bonding
Generate representative catalyst surface models
Calculate key properties and determine descriptors of ORR
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CASTEP
Data accumulation and storage in database
Work function
High throughput calculations: Overview
© 2009 Accelrys, Inc. 11
AxB1-x ensemble generation
Constrained atoms
1st layer `A`
2nd layer `B`
3rd layer `C`
4th layer `D`
A0B2C2D0
© 2009 Accelrys, Inc.
A1
A2
A3
A4
B1
B2
B3
B4
C1
C2
C3
C4
D1
D2
D3
D4
0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0
)!(!
!
kNk
N
k
N
−=
For a given supercell generate all
configurations with k out of N host
sites substituted by X atomsA0B2C2D0
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Define a configuration class by the
number of substitutions in each layer
Apply symmetry transformations
and find degeneracy of irreducible
configurations
Map each structure into a unique
binary string
Example Pt3Co: 6 layers slab setup
N=16, k=4
configurations
133 – non-equivalent configurations (due to symmetry)
Pt not stable on surface of Pt
A0 superclass contains
1820)!416(!4
!16=
−
© 2009 Accelrys, Inc.
A0 superclass structures
A0 superclass contains
Class Conf. x gi Class Conf. x gi Class
A0B4C0D0 1x1 A0B3C1D0 1x12+1x4 A0B2C2D0
A0B3C0D1 1x12+1x4 A0B2C1D1
A0B2C0D2
configurations
equivalent configurations (due to symmetry)
Pt not stable on surface of Pt3Co -> only consider A0 superclass
A0 superclass contains 42 irreducible configurations
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A0 superclass structures
A0 superclass contains 42 irreducible configurations
Conf. x gi Class Conf. x gi Class Conf. x gi
2x6+1x24 A0B1C3D0 1x4+1x12 A0B0C4D0 1x1
4x12+2x24 A0B1C2D1 4x12+2x24 A0B0C3D1 1x12+1x4
2x6+1x24 A0B1C1D2 4x12+2x24 A0B0C2D2 2x6+1x24
A0B1C0D3 1x12+1x4 A0B0C1D3 1x12+1x4
A0B0C0D4 1x1
Pt3Co: most stable configurations
© 2009 Accelrys, Inc.
E = E0
ba
E = E0 + 0.03 eV E = E0+ 0.04 eV
~11 configurations give significant contribution into the TD average.
Entropic factor may be important
999.0
96.0
/)(
11,1
11
/)(
4,1
4
0
0
==
==
−−
=
−−
=
∑
∑TkEE
j
j
TkEE
j
j
Bj
Bj
egZ
egZ
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c d
E = E0+ 0.04 eV E = E0+0.07 eV
~11 configurations give significant contribution into the TD average.
J. L. Gavartin et al., Transactions of the
Electrochemical Society 25(1) 1335-1344 (2009).
Surface phase diagram
• stoichiometry near the surface may significantly deviate from its nominal bulk value.
Understanding surface phase diagram is critical for
– assessing catalytic reactivity
– testing electrochemical stability
Pd3Co: The thermodynamic Co fraction in the
second and third layers is
Pt Co : The variation of Co fraction between the
thermodynamic fraction fk of metal X in the layer k
© 2009 Accelrys, Inc.
Pt3Co : The variation of Co fraction between the
layers is somewhat less pronounced.
Shuo Chen et al Am. Chem. Soc./ 2008, 130, 13818
stoichiometry near the surface may significantly deviate from its nominal bulk value.
Understanding surface phase diagram is critical for
Co: The thermodynamic Co fraction in the
second and third layers is overstoichiometric;
Co : The variation of Co fraction between the
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Co : The variation of Co fraction between the
layers is somewhat less pronounced.
Shuo Chen et al Am. Chem. Soc./ 2008, 130, 13818
Effect of lattice strain on oxygen adsorption
)(2
1)()( 2
* OEsurfaceEsurfaceOEEad −−+=
Compressive lateral strain leads to
approximately linear decrease of the
Oxygen adsorption energy, while lattice
expansion leads to an increase of Eads(O).
A similar trend was reported earlier for
Cu(111), Ru(0001) and Au(111) surfaces.
© 2009 Accelrys, Inc.
Cu(111), Ru(0001) and Au(111) surfaces.
Y. Xu, Surf. Sci., 494, 131-144 (2001).
M. Mavrikakis, Phys. Rev. Lett., 81, 2819 (1998).
M. Mavrikakis, Catal. Lett., 64, 101 (2000).
O adsorption on most stable (Pt/Pd)3Co
surfaces suggests some additional efects
besides strain, e.g. chemical modification
and surface relaxation.
Effect of lattice strain on oxygen adsorption
expansion leads to an increase of Eads(O).
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surfaces suggests some additional efects
besides strain, e.g. chemical modification
High throughput materials calculations
© 2009 Accelrys, Inc. 17
Creating the discovery database
© 2009 Accelrys, Inc. 18
Reporting and mining the database
© 2009 Accelrys, Inc. 19
Calculations database: Portal
Access via a Web Portal:
1. Choose the database name (local or remote)
2. Choose composition of a material of interest
3. Choose report tables to show
© 2009 Accelrys, Inc.
1. Choose the database name (local or remote)
2. Choose composition of a material of interest
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Calculations database: systems overview
Statistics for all selected jobs: Run time and CPUs used
Systems categorized as bulk, slab or molecule and shown by chemical composition
Choose the chemical composition of interest
© 2009 Accelrys, Inc.
Calculations database: systems overview
Statistics for all selected jobs: Run time and CPUs used
and shown by chemical composition
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Calculations database: Table of runs for a system
Sortable tables display key job information (a single calculation per line):
Choose the specific individual calculation to see all its details
© 2009 Accelrys, Inc.
Calculations database: Table of runs for a system
Sortable tables display key job information (a single calculation per line):
Choose the specific individual calculation to see all its details
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Calculations database: Job details
The details are given in different tables, that may be shown or hidden
Jmol visualiser for structure viewing, manipulation and analysis
© 2009 Accelrys, Inc.
The details are given in different tables, that may be shown or hidden
Jmol visualiser for structure viewing, manipulation and analysis
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Results details: Workfunction and d-band centre
© 2009 Accelrys, Inc.
band centre
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Oxygen Reduction Reaction
© 2009 Accelrys, Inc.
E
E0=E(O2+*)
ETS=E(O*-O*)
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Reaction coordinate
E1=E(O2*)
E2=2E(O*)
Ediss=E2-E1 Eads1=E1-E0
Ea=ETS-E1 Eads2=E2-E0
Eads1=E1-E0
iCatDesign
Reaction free energy protocol
•Calculate free energy of main steps of dissociative ORR reaction as
a function of cell potential U
On input:
File with energies
Cell Potential U
Substrate
O adsorbed
OH adsorbed
© 2009 Accelrys, Inc.
1. J.K. Nørskov, J. Rossmeisel, A. Logadottir, et al.J. Phys. Chem. B,108, 17866
OH adsorbed
H2O and H2 gas phase
Correction energies
(-ST, ZPE, solvation)
Reaction free energy protocol
Calculate free energy of main steps of dissociative ORR reaction as
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1. J.K. Nørskov, J. Rossmeisel, A. Logadottir, et al.J. Phys. Chem. B,108, 17866-17892 (2004).
Reaction free energy protocol
© 2009 Accelrys, Inc. 27
Summary
• A series of tools and models have been developed for screening various Pt alloy
combinations for stability and activity.
• Tools developed can be used to screen Pt and non
• ORR activity is improved by lattice strain (compressive for Pt)
• Strain is controlled by alloying with base metals antisegregating away from the
surface (typically metals with smaller atomic radius)
• D-band centre, surface segragation and adsorption energies are found to be useful
descriptors
© 2009 Accelrys, Inc.
descriptors
A series of tools and models have been developed for screening various Pt alloy
Tools developed can be used to screen Pt and non-Pt compositions
ORR activity is improved by lattice strain (compressive for Pt)
Strain is controlled by alloying with base metals antisegregating away from the
surface (typically metals with smaller atomic radius)
band centre, surface segragation and adsorption energies are found to be useful
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Conclusions: High Throughput Calculations
• Materials Discovery beyond the trivial case requires a vast number of systems to be studied, each requiring HPC computing itself.
• Successful projects require collaboration of different organizations and modeling with experiment.
• Require new strategies allowing for large multicollaborative projects providing automation in – optimization of calculations – strict quality control
© 2009 Accelrys, Inc.
– strict quality control– streamlined analysis and reporting– Data storage and mining in a flexible, extensible database
• Pipeline Pilot and the Materials Studio Collection have been used to– Build a framework for Materials HTC
• Automated job generation, execution and analysis• Datamining via web portal
– Screen >2000 catalyst leads and identify candidates for development– Provide a source for project teams to explore.
Conclusions: High Throughput Calculations
Materials Discovery beyond the trivial case requires a vast number of systems to be studied, each requiring HPC computing itself.
Successful projects require collaboration of different organizations and
Require new strategies allowing for large multi-platform and multi-user collaborative projects providing automation in
29
Data storage and mining in a flexible, extensible database
Pipeline Pilot and the Materials Studio Collection have been used toBuild a framework for Materials HTC
Automated job generation, execution and analysis
Screen >2000 catalyst leads and identify candidates for developmentProvide a source for project teams to explore.
Acknowledgements
• Dan Ormsby
• Amity Andersen
• David Gunn
• Arek Krzystala
• Victor Milman
• Patricia Gestoso-Suoto
J. L. Gavartin, M. Sarwar, D. C. Papageorgopoulos, D. Gunn, S. Garcia,
A. Perlov, A. Krzystala, D. L. Ormsby, F. Liu, G. Goldbeck
Andersen, S. French, D. Thompsett. Exploring fuell cell cathode
materials: High throughput calculation approach.
Transactions of the Electrochemical Society
© 2009 Accelrys, Inc.
Funding:
This project is partly funded under Technology Strategy Board Project Number:
/5/MAT/6/I/H0379C. The TSB is a business
established by the government. Its mission is to promote and support research into, and
development and exploitation of technology and innovation for the benefit of UK
business, in order to increase economic growth and improve the quality of life. It is
sponsored by the Department for Innovation, Universities and Skills (DIUS) (22).
J. L. Gavartin, M. Sarwar, D. C. Papageorgopoulos, D. Gunn, S. Garcia,
A. Perlov, A. Krzystala, D. L. Ormsby, F. Liu, G. Goldbeck-Wood, A.
Andersen, S. French, D. Thompsett. Exploring fuell cell cathode
materials: High throughput calculation approach.
Transactions of the Electrochemical Society 25(1) 1335-1344 (2009).
30
This project is partly funded under Technology Strategy Board Project Number:
/5/MAT/6/I/H0379C. The TSB is a business-led executive non-departmental public body,
established by the government. Its mission is to promote and support research into, and
development and exploitation of technology and innovation for the benefit of UK
business, in order to increase economic growth and improve the quality of life. It is
sponsored by the Department for Innovation, Universities and Skills (DIUS) (22).