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

摘要

Covellite (CuS) is a transition metal chalcogenide mineral, its structure can be described as a succession of planar CuS layers and Cu2S2 double layers. The success of the synthesis of the covellite nanoparticles enhanced their properties with potential applications in energy production and catalysis. Furthermore, covellite is involved in reactions of environmental importance and in the hydrometallurgical process for copper extraction. Investigations of the surface properties with relaxation/reconstruction are crucial for understanding its stability and chemical reactivity. Three different cleavage planes along (001) direction leading to the exposition of the sulfur and copper atoms were investigated under DFT/Plane Waves formalism. Five reconstructed/relaxed surfaces arising from the cleavage planes were studied. The C surfaces related to the Cu-S (trigonal planar) cleavage are the most favored. A stable planar graphene- like monolayer (1L-CuS) was predicted to exist from the large surface relaxation. Cu-Cu bonding was predicted to exist for the B surface related to the Cu(2)-S(2) cleavage with distances between 2.44 and 2.80 A. The [S4]~(2-) polysulfide was also formed in the B surface reconstruction indicating that the sulfur is oxidized leading to the reduction of the copper. Topological analysis (QTAIM and ELF) were performed to understand the nature of the chemical bonding and provide new insights about its chemical reactivity.