Inelastic Neutron Scattering and Theoretical Studies on Strontium Tungstate, SrWO4

Prabhatasree Goel ； R. Mittal ； Mayank K. Gupta ； Mala N. Rao ； S. L. Chaplot ； S. Rols ； A. K. Tyagi ； Zverev Petr

《Chinese Journal of Physics》 49卷1期 (2011/02) Pp. 308-315

並列摘要

We report inelastic neutron scattering measurements, lattice dynamics calculations, and molecular dynamics simulations on SrWO4. At ambient conditions, this compound crystallizes in a body-centered tetragonal unit cell (space group I4(subscript 1/a)) popularly known as the scheelite structure. We have developed transferable interatomic potentials to study the lattice dynamics of this class of tungstate compounds. The model parameters have been fitted with respect to the experimentally available Raman and infrared frequencies, elastic constants, and the equilibrium unit cell parameters. Phonon dispersion curves of acoustic branches along [100] symmetry direction have been measured using the Triple Axis Spectrometer at Dhruva reactor, India. The measured dispersion is in very good agreement with our calculated results. Phonon density of states has been measured for a polycrystalline sample using IN4C spectrometer at Institut Laue-Langevin, Grenoble. The measured phonon density of states is in excellent agreement with the theoretical calculations, thus validating the interatomic potential developed. Molecular dynamics simulations have been carried out to study the pressure-driven transformation of the scheelite phase of SrWO4. We have studied the behavior of the tungstate up to 100 GPa. Our calculated equation of state is in very good agreement with the reported experimental and first principles calculations. In our calculations, there appears to be a second transformation at around 45 GPa with a volume drop of about 8%, which hitherto had not been observed experimentally in this compound.