Raman scattering spectra of La3Ga5SiO14 (LGS) crystals

Based on the space group theory, the normal vibration modes of La3Ga5SiO14 (LGS) crystal were predicted, and the Raman scattering intensities of non-polar and polar modes were calculated respectively. The lattice vibration and structure of LGS crystal were investigated by Raman spectroscopy and density-functional theory (DFT). The DFT calculations were made on SiO4, GaO4, GaO6, La3Ga4O12 and La3Ga3SiO12 clusters, which model the atomic cluster in LGS crystal. Excellent agreement has been achieved between vibrational frequencies predicted by the theory and those observed in experiments. The layer structure of LGS crystal is identified, and its excellent piezoelectric properties are mainly attributed to the large polarizability anisotropy of La3Ga4O12 and La3Ga3SiO12 clusters, which results from the strong interaction between Ga(Si)O4 tetrahedras of LGS crystal. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)