Electronic structure study of the high-pressure vibrational spectrum of FeS ₂ pyrite

Plane-wave density functional calculations are used to investigate the pressure dependence of the geometry and F-point phonons of FeS ₂ pyrite up to 150 GPa. The linear response method is employed to calculate the vibrational properties. Raman-active modes are in excellent agreement with the experimental data available up to 50 GPa, ¹ and we predict the evolution with pressure of the IR-active modes for which no high-pressure spectroscopic data have been reported so far. Over the wide pressure range investigated here, all vibrational frequencies depend nonlinearly on pressure; their pressure dependence is quantified by determining the full set of mode Grüneisen parameters and their pressure derivatives.