Inelastic neutron scattering and lattice dynamics of AlPO4

A semi-empirical interatomic potential in AlPO4, previously determined using ab initio calculations has been widely used in studying the phase transitions among various polymorphs. We report here measurements of the phonon spectrum in low-cristobalite phase of AlPO4 using High-Resolution Medium-Energy Chopper Spectrometer at ANL, USA in the energy transfer range 0-160 MeV. The calculated phonon spectra using the available potential shows a fair agreement with the experimental data. However the agreement between the two is improved by including the polarizability of the oxygen atoms in the framework of a shell model. (author)