Calculation on surface energy and electronic properties of CoS ₂

Abstract

Density functional theory was employed to investigate the (111), (200), (210), (211) and (220) surfaces of CoS 2 . The surface energies were calculated with a sulfur environment using first-principle-based thermodynamics. It is founded that surfaces with metal atoms at their outermost layer have higher energy. The stoichiometric (220) surface terminated by two layer of sulfur atoms is most stable under the sulfur-rich condition, while the non-stoichiometric (211) surface terminated by a layer of Co atoms has the lower energy under the sulfur-poor environment. The electric structure results show that the front valence electrons of (200) surface are active, indicating that there may be some active sites on this face. There is an energy gap between the stoichiometric (220) and (211), which has low Fermi energy, indicating that their electronic structures are dynamically stable. Spin-polarized bands are calculated on the stoichiometric surfaces, and these two (200) and (210) surfaces are predicted to be noticeably spin-polarized. The Bravais–Friedel–Donnay–Harker (BFDH) method is adopted to predict crystal growth habit. The results show that the most important crystal planes for the CoS 2 crystal growth are (111) and (200) planes, and the macroscopic morphology of CoS 2 crystal may be spherical, cubic, octahedral, prismatic or plate-shaped, which have been verified by experiments.

Size-Dependent Thermodynamic Stability of Copper Sulfide Nanoparticles

“…Our results indicate that the (100) orientation with a stoichiometric ratio termination has the lowest surface energy (0.284 J/m 2 ), followed by the (210) orientation (0.419 J/m 2 ). Interestingly, while previous studies have systematically investigated the surface stability of pyrite FeS 2 , and CoS 2 , the surface energy of c - CuS 2 had not been reported so far. Therefore, this study provides a valuable complement to the surface science of pyrite-type compounds.…”

Revealing the intrinsic peroxidase-like catalytic mechanism of O-doped CoS2 nanoparticles

“…Considering the irregular shape of the NPs, especially some of the NPs had a quasi-spherical shape, the (001) and ( 111) faces may also be exposed on the surface. 36 In addition, the electron paramagnetic resonance (EPR) spectrum of O-doped CoS 2 NPs indicated that there were no sulfur vacancies in them (Fig. S4 †).…”

“…With an increased amount of oxygen doping, the edges of the NPs showed a tendency to lose their angles between different exposed surfaces. As the quasi-spherical NPs with mainly exposed facets of (001) and (111), 36 and the surface energy of (001) facet is lower than that of (111) facet, 42 the DFT calculation uses (001) facet as the model is reasonable.…”