Structure and dynamics of the Lu$_{2}$Si$_{2}$O$_{7}$ lattice: Ab initio calculation

The ab initio calculations have been carried out for the crystal structure and Raman spectrum of a single crystal of lutetium pyrosilicate Lu$_{2}$Si$_{2}$O$_{7}$. The types of fundamental vibrations and their frequencies and intensities in the Raman spectrum for two polarizations of the crystal have been determined. The calculations have been performed within the framework of the density functional theory (DFT) using the hybrid functionals. The ions involved in the vibrations have been identified using the method of isotopic substitution. The results of the calculations are in good agreement with the experiment.