First-Principles Study of Structural Stabilities, Electronic and Optical Properties of SrF₂ under High Pressure

An investigation of structural stabilities, electronic and optical properties of SrF₂ under high pressure is conducted using a first-principles calculation based on density functional theory (DFT) with the plane wave basis set as implemented in the CASTEP code. Our results predict that the second high-pressure phase of SrF₂ is of a Ni₂In-type structure, and demonstrate that the sequence of the pressure-induced phase transition of SrF₂ is the fluorite structure (Fm3m) to the PbCl₂-type structure (Pnma), and to the Ni₂In-type phase (P6₃/mmc). The first and second phase transition pressures are 5.77 and 45.58GPa, respectively. The energy gap increases initially with pressure in the Fm3m, and begins to decrease in the Pnma phases at 30GPa. The band gap overlap metallization does not occur up to 210GPa. The pressure effect on the optical properties is discussed.