Structural studies of CuAlSe₂ and CuAlS₂ chalcopyrites at high pressures

The ternary chalcopyrite compounds CuAlSe₂ and CuAlS₂ were studied up to 14.8 GPa in a diamond anvil cell by energy dispersive X-ray diffraction (EDXRD). The powder X-ray diffraction data at high pressure show that CuAlSe₂ undergoes a pressure-induced structural phase transition around 12.5 GPa from the chalcopyrite structure to NaCl type structure. CuAlS₂ exhibits structural stability up to 14.8 GPa. The pressure-induced structural phase transition observed in the EDXRD experiments is consistent with the theoretical total energy calculations. The results are consistent with the conclusions of a recent high-pressure Raman study reported for these compounds.