Concentration model of semiconductor-metal phase transitions in SmS

Model calculations explaining the mechanism of the semiconductor-metal phase transition in SmS are carried out. The model, slightly modified, draws upon methods employed earlier to account for the concentration mechanism of piezoelectric resistance and thermovoltaic effect in SmS. The stable results are obtained from calculations for the phase transition pressure under hydrostatic compression (P _c ～ 700 MPa at T = 300 K). On this basis, it is concluded that the 4f levels of samarium ions and their excited states determine the value of P _c . The proposed model is universal in character and can be applied to calculations of other effects in SmS, which are associated with Mott transitions and are accompanied by collective carrier delocalization.