First principles study of the structural, electronic and magnetic properties of w-CoS

Highlights: • w-CoS is mechanically stable. • The origin of the experimentally reported band gap is for the first time explained using DFT + U. • w-CoS is an indirect band gap semiconductor with band gap of about 1 eV. • w-Cos is anti-ferromagnetic. -- Abstract: We have employed density functional theory (DFT) to study the structural, mechanical, electronic structure and magnetic properties of wurtzite cobalt monosulphide (w-CoS). We established that within the framework of DFT, w-CoS is most stable in the anti-ferromagnetic phase but returns a metallic state contrary to the experimental reports. The cohesive energy, formation energy and elastic properties confirm that it is mechanically stable. Employing DFT with the on-site coulomb interaction term U, we established that w-CoS is an indirect band gap semiconductor with a possible direct band gap at the high-symmetry point A in agreement with experimental data. We also studied the dependence of magnetic moment of Co ion on the coulomb interaction term U and found that U values ranging from 5.5 eV to 8.0 eV best accounts for the wide range of the experimentally reported band gaps.