New high-pressure polymorph of In2S3 with defect Th3P4-type structure

Abstract

The high pressure behavior of β-In2S3 (I41/amd and Z=16) has been studied by in situ synchrotron radiation X-ray diffraction combined with diamond anvil cell up to 71.7GPa. Three pressure-induced phase transitions are evidenced at ~6.6GPa, ~11.1GPa at room temperature and 35.6GPa after the high-temperature annealing using a portable laser heating system. The new polymorph of In2S3 at 35.6GPa is assigned to the denser cubic defect Th3P4 structure (I4¯3d and Z=5.333), whose unit-cell parameters are a=7.557(1) Å and V=431.6(2) Å3. The Th3P4-type phase can be stable at least up to 71.7GPa and cannot be preserved at ambient pressure. The pressure–volume relationship is well described by the second-order Birch–Murnaghan Equation of State, which yields B0=63(3)GPa and B0′=4 (fixed) for the β-In2S3 phase and B0=87(3)GPa and B0′=4 (fixed) for the defect Th3P4-type phase respectively.