On the interpretation of the experimental Raman spectrum of β-eucryptite LiAlSiO 4 from atomistic computer modeling

Abstract

The vibrational spectrum of β-eucryptite LiAlSiO 4 with stuffed high quartz structure – commercially relevant for zero-expansion glass ceramics – was calculated by lattice energy minimization and diagonalization of the dynamical matrix using an ab initio based ion-pair shell model potential. A full symmetry analysis of the vibrational modes was carried out. Raman activity of vibrations was calculated under parameterization of individual polarizability factors for each type of interatomic bonds in β-eucryptite LiAlSiO 4. Calculated vibrational energies agree with the experimental energies within ±2.3%. Agreement of calculated spectroscopic Raman intensities with experimental intensities is within ±2% for the most intense vibrational modes, for other modes it is found to be still better than ±50%. An extensive description of the vibrational spectrum of β-eucryptite LiAlSiO 4 is given. A correlation analysis between the optical phonons in β-eucryptite and the structurally related β-quartz is given. A detailed analysis of the normal modes was carried out.