High pressure nanoarchitectonics and metallization of barium chloride and barium bromide.

As one of the most prototypical AX 2 -type compounds, barium halide shared the cubic structure with Fm -3 m symmetry for BaCl 2 or orthorhombic structure with Pnma symmetry for BaBr 2 at ambient pressure. In this work, we explored the crystal structures of BaCl 2 and BaBr 2 under high pressure. We predicted a thermodynamically more favored structure with orthorhombic Cmcm symmetry for both BaCl 2 and BaBr 2 , at 74 and 47 GPa, respectively. Our simulations reveal that the metallic feature of Cmcm BaCl 2 and Cmcm BaBr 2 under high pressure. The present results improve the understanding of high-pressure structures of AX 2 compounds at extremely high-pressure conditions.