Comparison of proton conduction in KTaO3 and SrZrO3

In the present paper, the authors focus on proton conduction pathways in a cubic perovskite KTaO3 and an orthorhombic perovskite SrZrO3. Density functional theory with a generalized gradient approximation is used to find proton binding sites. The nudged elastic band method is used to find transition states between minima. With this potential energy map of binding and transition states, adjacency matrices and their analogs identify four types of conduction paths in KTaO3. Distortions from these paths are seen in SrZrO3. In both cases, the lowest energy path has an intraoctahedral transfer rate-limiting barrier. A Fourier analysis of the OH stretch in ab initio molecular dynamics simulations revealed a strongly redshifted OH stretch in SrZrO3 relative to KTaO3. Hence, an orthorhombic system with a lowest energy conduction path limited by an intraoctahedral barrier can exhibit a redshifted OH stretch. (C) 2007 American Institute of Physics.