Phase transformation of BeSe and BeTe to the NiAs structure at high pressure

Abstract

We report the existence of a reversible pressure-induced first-order phase transition between the zinc-blende (B3) and the NiAs (B8) phase in the beryllium chalcogenides BeSe and BeTe at pressures of 56\ifmmode\pm\else\textpm\fi{}5 GPa and 35\ifmmode\pm\else\textpm\fi{}5 GPa, respectively. The NiAs phase remains stable in both compounds with further pressure increase up to at least 72 GPa in BeSe and 53 GPa in BeTe. For BeTe, an amorphous phase was observed upon decompression in the pressure range from 47 to 32 GPa. The equation of state is determined for each compound. We discuss the systematic trends of the structural phase transition, the stability of the NiAs structure, amorphization, as well as metallization in the beryllium chalcogenides.