Pressure-induced amorphization of covellite, CuS

Abstract

CuS, or covellite (hexagonal symmetry), was compressed in a diamond anvil cell at room temperature up to a pressure of 45 GPa, and studied using x rays from both a Mo Kα source and a synchrotron. The x-ray diffraction spectrum of CuS disappears by about 18 GPa. The presence of Cu fluorescence lines in all spectra and the reappearance of diffraction lines upon decompression confirm that CuS undergoes reversible pressure-induced amorphization at this pressure. A third-order Birch–Murnaghan equation of state fit to the diffraction data below 11 GPa yields a bulk modulus of 89±10 GPa with a pressure derivative of −2±2 for covellite. Further compression up to 45 GPa shows three to four diffraction lines of very low intensity, implying some high pressure ‘‘ordering’’ of the amorphous phase. The Raman spectra obtained indicate that the changes in structure are probably due to the twisting or the distortion of covalently bonded CuS4–CuS4 units in different directions.

Compression of klockmannite, CuSe

“…In comparison, the bulk modulus of CuS is 89Ϯ10 GPa with a pressure derivative of Ϫ2Ϯ2. 7 The higher the bulk modulus, the less compressible the compound. Therefore, CuSe is a more rigid structure than CuS, possibly due to the higher covalency of Cu-Se bonds in comparison with Cu-S bonds.…”

“…CuS undergoes a transition to an orthorhombic phase at a temperature of 55 K. 14 Since the effect of low temperature is thermodynamically similar to increased pressure, the mechanism by which CuS goes amorphous has been discussed as a kinetically hindered transition to the low temperature orthorhombic phase. 7 CuSe undergoes a similar transition to an orthorhombic phase, but at 323 K, a temperature higher than room temperature. 6 This transition then is due to an expansion effect as opposed to the effect of compression.…”

“…6 Isostructural CuS shows pressureinduced amorphization under high pressure, at 18 GPa. 7 Thus, we wanted to observe the effect of compression on the CuSe lattice.…”

The Stability and Structural, Electronic and Topological Properties of Covellite (001) Surfaces.

“…The Bader's topological analysis indicates that Cu(2)−S(1) bond is the weakest region in the CuS bulk . Mechanical strength analyses indicate that sulfur atoms drive the solid compressibility and its bulk modulus is similar to the chalcopyrite . At 55 K CuS undergoes structural phase transition to orthorhombic symmetry, however there is just a small slipping of the Cu(1) and Cu(2) layers in the structural arrangement and electronic properties are practically unchanged …”

A micro-interface route to CuS superstructure composed of intersectional nanoplates

“…After cessation of the stirring, the solvents are delaminated, and the product was deposited at the stable interface (Scheme 1d). The formation of a such superstructure may relate to the intrinsic layer structural features of covellite CuS [34], but the exact formation mechanism of such an intersectional structure on the organic-organic micro-interface remains unclear and needs more dedicated work in the future.…”