Ab initio study of 2H-MoS₂using Hay and Wadt effective core pseudo-potentials for modelling the (101̄0) surface structure

Abstract

Periodic Hartree-Fock and DFT methods were employed to calculate the geometric and electronic properties of bulk 2H-MoS 2 and of its catalytically important (101 0) edge structure. The core electrons of molybdenum and sulfur were represented by the effective core pseudo-potentials, developed by Hay and Wadt. For the calculations (101 0) type surface structures were generated by cutting sections from an 2H-MoS 2 crystal, which consists of four, six or eight rows of molybdenum and sulfur atoms. The calculated elastic constants follow the experimental constants and show that 2H-MoS 2 is an anisotropic covalent compound held together by weak dispersion interactions between neighbouring S-Mo-S units. The relaxation of the (101 0) surface of 2H-MoS 2 leads to an inner relaxation of the Mo atoms and the formation of weakly coupled surface S-S species. As a result of the surface relaxation, the electronic charge of the surface states is different to that of the bulk states: empty Mo d states move into the band gap, and the surface becomes a better electron acceptor. In all calculations the model consisting of six rows of sulfur and molybdenum atoms is the most favourable one, because it provides an accurate description of the 2H-MoS 2 surface structure and enables calculations at reasonable computation time. The calculations based on pseudo-potentials are in good agreement with all-electron calculations and confirm that, in contrast to the semiconducting bulk, the (101 0) 2H-MoS 2 surface has metallic properties.

First-Principles Study of Electronic and Elastic Properties of Hexagonal Layered Crystal MoS2 Under Pressure

“…For the hexagonal structure MoS 2 , it is reduced to five components, i.e., C 11 , C 12 , C 13 , C 33 , and C 44 . The calculated elastic constants are listed in Table 2, together with experimental [41] and previously calculated values [26,[42][43][44]. We obtain overall good agreement they seriously deviate from their nominal valence, these huge differences lie in that the Hirshfeld analysis is not a strict way in deciding the valence of an atom [39].…”

Energetics and electronic properties of defects at the (100) MoS2 surface studied by the perturbed cluster method

“…The HF method predicts a reduction of the fundamental band gap but the surface preserves semi-conducting properties, while the DFT method predicts the first two layers to be conductive [7,24]. The present EMBED01 calculations (with correlation correction) demonstrate that the Mo and S edges remain semi-conducting, despite the fact that the HOCO-LUCO gap decreases considerably.…”

“…It has been shown that six to eight layers along the (1010) direction reproduce the bulk properties at the center of the slab and give an accurate description of the surface [24]. The calculations revealed that Mo surface atoms relax inwards, while the exposed sulfur atoms relax outwards and toward each other across the S-Mo-S layer.…”

Effect of Cu2+ activation on interfacial water structure at the sphalerite surface as studied by molecular dynamics simulation

“…Much research based on MDS has been reported on water structure and the dynamic and thermodynamic characteristics of water at mineral surfaces (Du and Miller, 2007a;Gallo et al, 2002;Kalinichev and Kirkpatrick, 2002;Lee and Rossky, 1994;Rustad, 2001;Rustad et al, 2003;Spohr et al, 1999;Wang et al, 2004). Recently, quantum chemical calculations providing electronlevel information about atomic interactions, such as Density Functional Theory (DFT), have also been used in the study of sulfide minerals, such as molybdenite (Todorova et al, 2004) and pyrite (Blanchard et al, 2007;Hung et al, 2003;Zhao et al, 2014). However, due to the magnitude of the DFT calculation, it is difficult to study the interfacial water structure using DFT when compared to MDS.…”