Phonon Spectrum of La2Ge2O7: Ab Initio Calculation

Within the density functional theory, ab initio calculation of the crystal structure, phonon spectrum, and elastic properties of lanthanum germanate La2Ge2O7 with triclinic structure (space group PT, no. 2). Frequencies and types of fundamental vibrations are determined. The degree of involvement of ions in each mode is determined by analyzing calculated displacement vectors. The calculations are performed for the first time. Experimental data on IR and Raman spectra, as well as elastic constants of La2Ge2O7 are absent in the literature. The program CRYSTAL17 intended for ab initio calculations of periodic structures within the MO LCAO (molecular orbital as a linear combination of atomic orbitals) approach is used.