High pressure powder X-ray diffraction study of Cr2As and pressure-induced structural phase transition

Cr2As, which is an intermetallic compound of Cu2Sb-type with Strukturbericht designation C38 was studied under a pressure of up to 32.5 GPa at room temperature using in situ synchrotron X-ray powder diffraction with a diamond anvil cell. From the X-ray diffraction analysis, our results showed that the Cu2Sb (C38)-type phase of Cr2As undergoes a pressure-induced structural phase transition near 15.4 GPa. The high-pressure (HP) phase of Cr2As is suggested as an orthorhombic structure. No additional structural phase transition was observed up to 32.5 GPa, and the initial low-pressure (LP) Cu2Sb (C38)-type structure was recovered as the pressure was released, implying that the observed pressure-induced structural phase transformation was reversible. The pressure–volume data of Cr2As was fitted to a second-order Birch–Murnaghan equation of state, which yielded a bulk modulus of B0=125(3)B0=125(3) and 340 (12) GPa for the LP and the HP phases, respectively. Furthermore, the aa axis is more compressible than the cc axis for the LP phase of Cr2As. The anisotropic compressibility of the studied crystal is discussed in terms of the crystallography stacking.

► Cr2As undergoes a pressure-induced structural phase transition near 15.4 GPa.
► The observed pressure-induced structural phase transformation was reversible.
► The high-pressure (HP) phase of Cr2As was suggested as orthorhombic structure.
► The aa axis is more compressible than the cc axis for LP phase of Cr2As.