A First-principles Study of Ionic Conductivity in Superionic Solids

Brandon Wood, Massachusetts Institute of Technology

First-principles molecular dynamics simulations are well suited to the study of conductivity in superionic solids, thanks to the high frequency of diffusion events observable within reasonable simulation timescales. We carry out extensive Car-Parrinello simulations on supercells comprising between 54 and 112 atoms to investigate two paradigmatic case studies: AgI, a classic example of a superionic solid; and CsHSO4 , an anhydrous superprotonic conductor with promising fuel cell applications. A combination of static, linear-response, and molecular dynamics calculations, as well as close examination of maximally localized electronic orbitals, allows us to characterize the structural, dielectric, and vibrational properties of these systems, as well as diffusion coefficients and ionic conductivities. The dynamical simulations offer a unique and unbiased characterization of the mechanisms of ionic diffusion and the statistics of most-traveled pathways, together with the detailed atomistic processes involved.

Abstract Author(s): Brandon Wood<br />Nicola Marzari<br />Department of Materials Science and Engineering, MIT