Relaxation of the Excess Free Volume of the Phase Transformation at the Phase Interface between the Crystal and the Melt

The paper analyzes the excess free volume relaxation mechanism of the phase transformation, which is realized in the local dilatation region at the phase interface between the crystal and the melt. It also examines the structural state of phase interface and its influence on the phase interface mobility under pressure, applied during crystal growth from the melt. The paper explains the extreme impact of pressure on the mobility of phase interface. It also discusses the possibility of the phase interface reaching a state of anomalously high mobility under “optimal” pressure (referred to as “ultra-mobility”). As part of the mechanism of viscous flow of melt into the local dilatation region at the phase interface, arising in the crystallization process, a quantitative agreement with the experimental value of the “optimal” pressure, which ensures the extreme nature of the crystal–melt phase interface mobility, has been obtained.