The effect of the correlation and exchange interactions on the electronic and magnetic properties of the hexagonal NiS using the onsite exact exchange/hybrid functionals

We have performed ab initio calculations using the onsite exact exchange/hybrid functionals within the density functional theory to study the effect of the correlation and exchange interactions on the structural, electronic and magnetic properties of the hexagonal nickel sulphide (NiS) by varying the Fock exchange parameter value. The Perdew- Burke- Ernzerhof (PBE) calculation shows that the non magnetic state is the most stable, but the application of the onsite exact exchange/hybrid functionals for the correlated d electrons leads to get the anti-ferromagnetic AFM I state the most stable which is consistent with the experimental results. To get the semiconductor state we should use a alpha parameter value more than 0.05 which represents 5% of the Fock exchange. The alpha parameter has a big effect on the unit cell volume but there is a little effect on the c/alpha ratio. The magnetic moment and band gap are widely influenced by the exchange and correlation interactions. We have also investigated the effect of the lattice parameters on the magnetic and electronic properties.