О критической точке плавления простого вещества

Abstract

Based on the three-phase model of simple matter reviewed to the appearance and disappearance of the S-loop of a phase transition (PT) of the first kind on isotherme of state equation in the range of PT crystal-liquid (C-L). Calculations performed for argon showed that the S-loop of PT C-L on the isotherm of the state equation arises due to a sharp decrease and subsequent increase in pressure associated with the appearance of delocalized atoms at an isothermal increase in the specific volume. With an increase in temperature on the isotherm, the pressure associated with the delocalization of atoms passes from the negative region (where it compressed the system) to the positive region (where it stretches the system). This behavior of this function leads both to the appearance of the S-loop of the C-L PT on the isotherm of the equation of state, and to the disappearance of the S-loop of the C-L PT at high temperatures with the formation of the critical point of the C-L PT. The change in the parameters of the critical point of PT C-L with a decrease in the number of atoms in the nanosystem is studied. It is shown that during the transition to the nanosystem, the critical temperature and pressure decrease, and the critical molar volume increases. Calculations in the framework of the three-phase model of a simple matter showed that the structure at the critical point of PT C-L is close to an amorphous packing. At the same time, with a decrease in the number of atoms in the nanosystem, the parameters of this amorphous structure at the critical point of PT C-L change slightly.