A THEORETICAL MODELING OF THE STATIC AND DYNAMIC POLARIZABILITY OF O2- IN LARGE AND COMPLEX OXIDES

A time-dependent approach is employed in conjunction with a crystal po tential model to study the environment-specific optical linear respons e of the O2- ions in a number of cubic oxides with varying number of c onstituents, unit-cell dimension and degree of complexity. It is shown that the static polarizability of the anion may vary significantly de pending on the position of the anion within the unit-cell. Due to negl ect of overlap compression, our method has limited success in predicti ng the refractive indices of large crystals of complex structures. For small binary oxides the frequency-dependent polarizability of the O2- ion is found to exhibit the first poles close to the ultraviolet abso rption edges ascribed to the lowest excitonic transitions in these cry stals.