High-pressure and thermal properties of #gamma#-Mg_2SiO_4 from first-principles calculations

摘要

First-principles density-functional approach was used to obtain the crystal parameters and phonon spectra of #gamma#-Mg_2SiO_4 (spinel and ringwoodite) as functions of pressure. The Gruneisen parameters at the #GAMMA# point were obtained and compared with the experimental data. Using quasiharmonic approximation, the total free energy of the crystal was calculated as a function of volume for several temperatures, hence, the buil modulus and thermal expansion were found as a function of temperature. A good agreement between calculated and experimental values was obtained in a wide temperature range.