Crystal structure of HgGa₂Se₄ under compression

Highlights: ► Single crystals of HgGa₂Se₄ with defect-chalcopyrite structure were synthesized. ► HgGa₂Se₄ exhibits a phase transition to a disordered rock salt structure at 17 GPa. ► HgGa₂Se₄ undergoes a phase transition below 2.1 GPa to a disordered zinc blende. - Abstract: We report on high-pressure x-ray diffraction measurements up to 17.2 GPa in mercury digallium selenide (HgGa₂Se₄). The equation of state and the axial compressibilities for the low-pressure tetragonal phase have been determined and compared to related compounds. HgGa₂Se₄ exhibits a phase transition on upstroke toward a disordered rock-salt structure beyond 17 GPa, while on downstroke it undergoes a phase transition below 2.1 GPa to a phase that could be assigned to a metastable zinc-blende structure with a total cation-vacancy disorder. Thermal annealing at low- and high-pressure shows that kinetics plays an important role on pressure-driven transitions