Manganese chalcogenides are being actively studied both experimentally and theoretically because of the metal-to-insulator transition under pressure and possible catalytic, optical and magnetic applications [1,2,3]. In particular, binary manganese sulfide MnS was found in several crystal phases: α–γ-MnS. The α-MnS phase crystallizes in cubic structure (Space Group Fmm), and γ-MnS–in hexagonal structure (SG P63mc). It is known that γ-MnS is metastable when heated to 200–300 °C; it becomes the α-MnS phase [1]. We carried out our theoretical studies of this compound taking into account the antiferromagnetic ordering of the manganese ions at the ambient conditions and in compressed unit cells. To study the electronic structure of MnS, our calculations were done in the Quantum ESPRESSO software package [4] using the DFT + U method [5] for the Pedew-Burke-Ernsenhof (PBE) form of the exchange–correlation function [6]. MnS is a wide-band insulator in environmental conditions. In the course of the study, it was found out that in order to reproduce a wide gap, strong electron correlations should be taken into account. Thus, to obtain the experimental value of the band gap, the values of the Coulomb interaction parameter U = 6.9 eV and the exchange interaction J = 0.86 eV were taken. It is also worth noting that taking into account electron correlations affects the γ-MnS more strongly and when the maximum parameter of the Coulomb interaction parameter U = 6.9 eV is reached; the width of the electron gap of the γ-MnS reaches about 2 eV, while the α-MnS has a band gap width of no more than 1 eV. For compressed volumes of the unit cell, it was found that with increasing pressure on the unit cell, the band gap width decreases and finally closes for the cell volume, which is about 50% of the ambient volume. Thus, the closure of the energy gap and the increase in metallic states at the Fermi energy demonstrate the experimentally observed transition from insulator to metal in MnS.
Supplementary Materials
The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ASEC2022-13784/s1, Conference poster.
Author Contributions
Conceptualization, A.L.; methodology, E.C. and A.L.; software, E.C.; validation, A.L.; investigation, E.C.; writing—original draft preparation, E.C.; writing—review and editing, A.L.; supervision, A.L.; project administration, A.L. All authors have read and agreed to the published version of the manuscript.
Funding
This research was supported within the state assignment of the Ministry of Science and Higher Education of the Russian Federation (theme “Electron” No. 122021000039-4) and partially by Russian Foundation for Basic Research (project 20-02-00234).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available on request from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
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