Crystal structure and vibrational spectrum of copper mercury ortho‐thiophosphate CuHgPS4

Abstract The compound CuHgPS 4 crystallizes in the orthorhombic system, space group Pna2 1 (No. 33), Z = 4, with lattice parameters a = 12.660(3), b = 7.3498(7), c = 6.0943(4) Å, and δ calc = 4.96 g/cm 3 . The title compound is stable in air and moisture and behaves as a semiconductor. The crystal structure consists of discrete tetrahedral PS 4 3‐ anions joined together by Cu + and Hg 2+ cations. The arrangement of the sulfur atoms is approximately hexagonal close‐packed in which P, Cu, and Hg occupy tetrahedral sites. The PS 4 , HgS 4 , and CuS 4 tetrahedra are slightly distorted with mean distances d(P‐S) = 2.055, d(Hg‐S) = 2.524, and d(CuS) = 2.320 Å, and 8% of the Hg atoms were found to be disordered, occupying interstitial tetrahedral sites. The title compound is isotypic to AgZnPS 4 and can be considered to be a defect structure of Enargite (Cu 3 AsS 4 ), which is a substitution derivative of the Wurtzite (ZnS) structure. The CuHgPS 4 vibrational spectrum has been recorded. The internal modes experimentally observed are in accord with the factor group prediction. A tentative assignment of the vibrational frequencies is proposed.