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 B-0 = 125(3) and 340 (12) GPa for the LP and the HP phases, respectively. Furthermore, the a axis is more compressible than the c axis for the LP phase of Cr2As. The anisotropic compressibility of the studied crystal is discussed in terms of the crystallography stacking. (C) 2011 Elsevier Ltd. All rights reserved.