Structural stabilities, electronic and optical properties of CaF2 under high pressure: A first-principles study

The structural stabilities, electronic and optical properties, the pressure-induced metallization for CaF2 have been studied by using the density functional theory calculations. The ground Fm (3) over barm phase is predicted to transform into Pnma structure at 8.1 GPa, which is well consistent with the experimental findings. Above 278 GPa, Pnma-CaF2 transform into P6(3)/mmc phase. The calculated structural data for Fm (3) over barm and pnma phases are in very good agreement with experimental values. The electronic band structures show that Pnma and P6(3)/mmc phases of CaF2 are insulators at the transition pressure. Upon further compression, the band gap of P6(3)/mmc decreases with pressure, and CaF2 is predicted to undergo metallization around 2250 GPa. The possible reason for the metallization was discussed. All CaF2 polymorphs have ionic character between Ca-F bond with the analysis of the charge-density distribution and density of states. (C) 2009 Elsevier B.V. All rights reserved.