Hydrogen and Lithium Rich Solids Under Pressure

Eva Zurek, SUNY at Buffalo, DMR 1005413

1. Band structure of the most stable RbH5 system, along with two filled molecular orbitals (MOs) of H3

- which make up these bands.

2. Front and side views of one of the most stable Li5H structures, highlighting the Li8H clusters of which it is comprised.

An evolutionary algorithm developed in our group, XtalOpt, has been used to predict a number of novel crystal structures which are stable under pressure. Calculations based upon density functional theory have elucidated the properties of these systems. Such materials can be synthesized in diamond anvil cells and have the potential to be superconductors or to be used in energy applications.

1. At pressures of only a few GPa, KHn, RbHn and CsHn (n > 1) are found to be stable. The lowest energy structures contain the linear H3

- units, the simplest example of a 3-center 4-electron bond.

2. Between 50-100 GPa the lithium subhydrides, LimH, 4 < m < 9, are predicted to be stable. These lithium rich systems are semimetallic and are composed of fused Li8H clusters.

MOs of H3-

Open Source Software for Structure Prediction

Eva Zurek, SUNY at Buffalo, DMR 1005413

We have released two major updates, versions 7 and 8 of XtalOpt, which is an evolutionary algorithm that incorporates the results of quantum mechanical calculations, as well as those using interatomic potentials, in order to determine the most stable geometries or crystal structures of solids. XtalOpt has been written as an extension to the molecular editor Avogadro, and released under the open-source GNU Public license. To date the Windows binary of XtalOpt has been downloaded over 800 times from the open-molecules website.

Dr. Zurek is a mentor in the ‘Undergraduate Research Group Experiences (URGE) in Computational Mathematics’ Program. Three female math majors are carrying out a year long research project in her group.URGE to Compute Cohort