Structural and elastic properties of defect chalcopyrite HgGa2S4 under high pressure

• Single crystals of HgGa 2 S 4 with defect-chalcopyrite (DC) structure were synthesized. • High-pressure X-ray diffraction in DC-HgGa 2 S 4 was performed. • Equation of state of DC-HgGa 2 S 4 determined (bulk modulus of 48.4 GPa). • Calculated elastic constants of DC-HgGa 2 S 4 reported at different pressures. • DC-HgGa 2 S 4 becomes mechanically unstable above 13.8 GPa. In this work, we focus on the study of the structural and elastic properties of mercury digallium sulfide (HgGa 2 S 4 ) at high pressures. This compound belongs to the family of AB 2 X 4 ordered-vacancy compounds and exhibits a tetragonal defect chalcopyrite structure. X-ray diffraction measurements at room temperature have been performed under compression up to 15.1 GPa in a diamond anvil cell. Our measurements have been complemented and compared with ab initio total energy calculations. The axial compressibility and the equation of state of the low-pressure phase of HgGa 2 S 4 have been experimentally and theoretically determined and compared to other related ordered-vacancy compounds. The pressure dependence of the theoretical cation–anion and vacancy-anion distances and compressibilities in HgGa 2 S 4 are reported and discussed in comparison to other related ordered-vacancy compounds. Finally, the pressure dependence of the theoretical elastic constants and elastic moduli of HgGa 2 S 4 has been studied. Our calculations indicate that the low-pressure phase of HgGa 2 S 4 becomes mechanically unstable above 13.8 GPa.