Synthesis, structure, elastic properties, lattice dynamics and thermodynamics of YVO_4 polymorphs from experiments and density functional theory calculation

摘要

Pure zircon and scheelite YVO_4 were prepared by solid state reaction and high-pressure route, respectively. Calculated structural parameters, bulk modulus and elastic constants show good agreement with experimental results. Calculated phonon dispersions show that zircon and scheelite YVO_4 are dynamically stable. Raman frequencies were determined and assigned to different modes according to the calculated results. After phase transition from zircon to scheelite, V-0 bond length becomes longer and shows more ionic characteristic, which leads to smaller discrepancy of V atoms' Born effective charge from their nominal charge and the shift downward of the internal modes frequencies. Thermodynamic properties of YVO_4 polymorphs were accurately predicted by quasi-harmonic approach.