Composition and temperature dependent electronic structures ofNiS2−xSexalloys: First-principles dynamical mean-field theory approach

Abstract

We investigate the evolution of the electronic structure of ${\mathrm{NiS}}_{2\ensuremath{-}x}{\mathrm{Se}}_{x}$ alloys with varying temperature and composition $x$ by using the combined approach of density-functional theory and dynamical mean-field theory. Adopting realistic alloy structures containing S and Se dimers, we map their electronic correlation strength on the phase diagram and observe the metal-insulator transition (MIT) at the composition $x=0.5$, which is consistent with the experimental measurements. The temperature dependence of the local magnetic susceptibility is found to show a typical Curie-Weiss-like behavior in the insulating phase while it shows a constant Pauli-like behavior in the metallic phase. A comparison of the electronic structures for ${\mathrm{NiS}}_{2}$ and ${\mathrm{NiSe}}_{2}$ in different lattice structures suggests that the MIT in this alloy system can be classified as of bandwidth-control type, where the change in the hybridization strength between Ni $d$ and chalcogen $p$ orbitals is the most important parameter.