Crystal structure of the high-pressure phase of BaFCl

Abstract

The structural stability of the layered matlockite compound BaFCl has been studied under pressure to \ensuremath{\sim}35 GPa. BaFCl is observed to undergo a reversible structural transition at about 22 GPa and the high-pressure phase has been identified to be monoclinic with space group ${P2}_{1}/m.$ The structural identification of the high-pressure phase was carried out by taking into account the fact that the interlayer bonding between the two similar ${\mathrm{Cl}}^{\mathrm{\ensuremath{-}}}$ layers is relatively weak compared to those between the other layers and intralayer bondings, thereby rendering the low-pressure structure unstable against the deformation under pressure.