High pressure-induced phase transitions in CdS up to 1 Mbar

Abstract

The pressure-induced structural transformations of CdS have been investigated using synchrotron x-ray diffraction in a diamond anvil cell up to 104 GPa and the density functional theory calculations. The x-ray diffraction experiments show that CdS is stable with the wurtzite-type structure at ambient conditions. The wurtzite-type phase transforms to NaCl-type structure at 3 GPa, which is followed by a second phase transition at 52.3 GPa. In the diffraction patterns, the peak-splitting is observed, indicating that the high-pressure phase appearing at 52.3 GPa is the Pmmn structure, rather than the Cmcm phase reported earlier. With increasing pressure, the lattice parameter a of the Pmmn phase increases abnormally, contrary to decrease of b and c axes. Our calculations reveal that the abnormal change of the a-axis could be related to the pressure-induced crystal structural change. The bulk modulus (B0), is 64.3(9) GPa for wurzite-type phase, 105(2) GPa for NaCl-type phase, and 54(4) GPa for the Pmmn phase, respectively.