The importance of steric effects in the insertion compounds of transition metal oxides
Abstract In this communication we report on Quantum Mechanical, ab initio calculations, to investigate the migration of Na and K ions in the hexagonal tungsten bronzes. Comparison of the migration profile calculated for the bronzes with an idealised, Coulomb-only, description of the interaction between inserted ion and host oxide, allows a direct estimate of the steric repulsion energy; it is negligible in the case of Na, while it is calculated as 0.52 eV per inserted K ion in hexagonal K 0.33 WO 3 .