The construction and application of a fully flexible computer simulation model for lithium oxide

An aspherical ion model (AIM) is constructed for lithium oxide, Li(2)O. The model incorporates both many-body polarization and short-range ion distortion effects. A procedure for extracting the required model parameters by fitting to results from a series of electronic structure calculations is described. The model is tested with respect to both static and dynamic properties. The experimentally observed Cauchy violation in the elastic constants and phonon frequencies are well reproduced as is the onset temperature for superionic behaviour in the Li(+) sublattice. The system is shown to display a peak in the heat capacity as a function of temperature. The correlated and uncorrelated ion dynamics are studied and the origin of the respective solid- and liquid-state Haven ratios is rationalized.