Correlation effects and band gap in manganese sulfide phases

Manganese sulfide (MnS) in the nanocrystalline state is being actively studied experimentally because of perspec-tive applications in catalysis, optical and magnetic materials [1]. In the course of our study, theoretical calcula-tions of the electronic structure and magnetic properties were carried out using the DFT+U method for several crystal phases of this compound: $\alpha$-MnS, $\beta$-MnS, $\gamma$-MnS. The $\alpha$-MnS phase crystallizes in the cubic structure with the space group Fm3m, $\beta$-MnS – in the cubic structure F$\stackrel{\_}{4}$3m, and $\gamma$-MnS – in the hexagonal structure P6$_{3}$mc [2]. It is known that $\beta$-MnS and $\gamma$-MnS modifications are metastable, when heated to 200-300°C collapse into the $\alpha$-MnS phase. To account for strong electronic correlations in the Mn 3d shell, we used several values of the direct Coulomb interaction parameter U ranging from 3 to 6.9 eV and the exchange interaction parameter J equal to 0.86 eV. In our DFT+U calculations, it was found that the $\alpha$-MnS and $\gamma$-MnS phases are insulators, and with the increase in the Coulomb interaction parameter, the electron density of the $\alpha$-MnS and $\gamma$-MnS phases was redistributed, resulting in an increase in the band gap at the Fermi level. In its turn, our calculations for the $\beta$-MnS phase resulted in the redistribution of the electron density but without the band gap. Thus, our theoreti-cal studies revealed significant electronic correlations in the binary compound – manganese sulfide MnS, it is important to take electronic correlations into account in MnS in order to obtain the insulator state. The studies were supported by the Russian Foundation for Basic Research, project grant No. 20-02-00234.

[1] Yongfu Tang, Teng Chen and Shengxu Yu, Chem. Commun., \textbf{51}, 9018 (2015).
[2] S. S. Aplesnin, O. B. Romanova, A. I. Galyas, V. V. Sokolov, Phys. Solid State, \textbf{58}, 1 (2016).