Electronic structure of pyrite-type manganese disulphide $\left(p{\mathrm{MnS}}_2\right):$ An ab initio study

The linear combination of atomic orbitals as implemented in the CRYSTAL95 code has been used to obtain the electronic structure of the pyrite-type manganese disulphide in the ferromagnetic state. Calculations made at the unrestricted Hartree-Fock (UHF) and local density approximation levels show that this compound has a larger ionic character within the HF approach. The band structures obtained with both methods of calculation are significantly different. In particular, the valence band is mainly occupied by the $p$ orbitals of sulfur in the UHF approach and the compound is described as an insulator, whereas, at the LDA level, the Mn $d$ orbitals also lie in this band and the compound then has a conductor character.