First-Principles Study Of The Thermodynamic And Vibrational Properties Of Res2 Under Pressure

Density functional theory is used to investigate the effect of hydrostatic pressure on the structural, energetic, electronic, and vibrational properties of bulk ReS2. The phase transition from the distorted 1T phase to the high-pressure distorted 1T' phase is rationalized based on the evaluation of their thermodynamic potentials. The electronic band gap of the 1T phase is shown to undergo a nearly direct to indirect transition at about 9 GPa, while the 1T' phase is found to remain a robust nearly direct band-gap material under pressure. The computational analysis of the vibrational properties of both ReS2 phases reproduces existing experimental Raman spectroscopy data for omega vs P trends and provides a path towards an accurate phase discrimination using infrared spectroscopy, inelastic neutron, and x-ray scattering.