Metal-nonmetal transition in NiS under pressure

The thermodynamical model of Lidiard for an itinerant antiferromagnet is extended to involve the strain energy and the volume dependence of the energy gap between up- and down-spin bands. The model is manipulated to fit the pressure effect of metal-nonmetal transition temperature and its first-order characteristics in NiS. Here, the volume compressibility used is measured to be 1.1×10−3 kbar−1. Changes in magnetic moment on the Ni sublattice and in enthalpy at the transition temperature are calculated from the obtained parameters and compared with the available experimental data. The nature of metal-nonmetal transition in NiS under pressure is discussed. Present study constitutes the first attempt to understand the energetics of the metal-nonmetal transition in NiS throughout its T-P diagram.