[Quantum chemistry ab initio calculation study on microstructure and raman spectra of phosphosilicates]

Quantum chemistry ab initio calculation was applied to study the hyperfine structure of ternary alkali phosphosilicates. Restricted Hartree-Fock method (RHF) with the basis sets of 6-31G(d) was employed to optimize geometric structure and calculate Raman spectra of a series of phosphosilicates model cluster structural units. Stress index of tetrahedron (SIT) was introduced to describe and classify the microstructure of ternary alkali phosphosilicates in order to investigate the effect of phosphorus-oxygen tetrahedron on the micro-environment of silicon-oxygen tetrahedron. It was suggested that the calculated vibrational wavenumbers of symmetric stretching vibration of non-bridging oxygen (NBO) depend not only on the species of the silicon-oxygen tetrahedron, which was called primary structure units, but also on the linkage of the neighboring tetrahedron and ring types. The phosphorus-oxygen tetrahedron exhibits regulative ability of bond angle and conductive ability of stress, so that the vibrational wavenumbers of silicon-oxygen tetrahedron are insensitive to the bond angle. It demonstrated that vibrational wavenumbers of NBO stretching vibration in the high frequency range show linear relationship with the value of SIT.