Sevenfold Coordinated MgSe: Experimental Internal Atom Position Determination to 146 GPa, Diffraction Studies to 202 GPa, and Theoretical Studies to 500 GPa

Abstract

MgSe has been studied using energy dispersive x-ray diffraction to 202 GPa and local density approximation and ultrasoft pseudopotentials to 500 GPa. MgSe undergoes a "continuous" phase transformation from the rocksalt to FeSi (B28) beginning at around 99 +/- 8 GPa and approaching sevenfold coordination at 202 GPa. Theoretical computation finds the B28 transition beginning at 58 GPa followed by a transition to an orthorhombic distortion of the B2 structure at 429 GPa. [S0031-9007(98)07261-5].