Chinese Acad Sci, Beijing Synchroton Radiat Facil, Inst High Energy Phys, Beijing 100049, Peoples R China
; Peking Univ, Dept Geol, Beijing 100871, Peoples R China
An investigation into the structural stabilities and the electronic and optical properties of CaF2 under high pressure was conducted using first-principles calculations based on density functional theory. Our results demonstrate that the sequence of the pressure-induced phase transition of CaF2 is the fluorite structure (Fm3m), the PbCl2-type structure (Pnma), and the Ni2In-type structure (P6(3)/mmc). At these phase transformations, the coordination number of Ca2+ increases from eight to nine and then to eleven. The mechanisms of the structure change were revealed from the PbCl2-type phase to the Ni2In-type phase. The energy band gap increases with pressure in the Fm3m and the Pnma phases, but decreases in the P6(3)/mmc phase. The band gap pressure coefficients were obtained using a linear pressure-dependent fit function. In addition, the energy band overlap metallization does not occur up to 218 GPa. The static dielectric constants epsilon(0) vs pressure are also discussed.