We report results of minimum-basis Pseudopotential Hartree-Fock studies of MI4-3 clusters (M = Na+, K+, Ag+, and Cu+), and of HgI4-2. The calculations are designed to characterize local-site effects on mobility paths in solid state electrolytes. We observe qualitatively correct behavior, with Ag+ predicted to be the most mobile ion. Quadrupolar polarizability of the metal ion, which is produced by s-d mixing, lowers the energy of trigonal transition state, thus accounting for the observation that quadrupole polarizable species are ideal mobile ions in close-packed halide frameworks. Mulliken populations show that there is considerable local covalency, so that electrostatic potential studies must be done very carefully. Expansion of the I4 tetrahedron lowers the barrier energy.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics