Pseudocritical point on the melting curve of a metastable phase

Abstract

The possibility of the existence of a limit to which the melting curve can be extrapolated into the metastable region is discussed. The analysis is made for the example of GaSb, for which the stable and metastable phases of the T-P diagram are known. When the melting curve of the high-pressure modification is extrapolated to low pressures, it crosses the curve of complete instability of the disordered phase at a point k. Since the melting curve is a line of equilibrium between two phases, one of which ceases to exist at the point k because the minimum of the thermodynamic potential that corresponds to this phase becomes degenerate, the melting curve terminates at the point k and further extrapolation of the curve is physically meaningless.