Structure and vibrational properties of alkali phosphate glasses from ab initio molecular orbital calculations

We have carried out ab initio molecular orbital calculations on clusters of atoms modeling the local structure of lithium and sodium metaphosphate glasses to investigate their structure and vibrational properties. The optimized structural parameters and O 1s photoelectron energies calculated at the Hartree–Fock/3-21G* level are in good agreement with the observed ones. We then performed frequency calculations for the lithium metaphosphate cluster. The calculated Raman spectrum agrees with the experimental one. On the basis of the calculated results, we interpret the vibrational spectra of alkali phosphate glasses and discuss the local coordination environments of alkali cations in the glassy system.