A thermodynamic approach to T–Pphase diagrams of substances in liquid and amorphous states

Abstract

The metastable phase equilibria of substances in thedisordered, liquid or amorphous, state are considered in T–Pcoordinates. Application of the thermodynamic model of pseudo-binarysolutions is illustrated by means of calculated metastable T–Pphase diagrams of water, carbon, and semiconducting compounds, GaSb andGa38Sb38Ge24. All calculated diagrams include the equilibrium linesbetween the disordered phases terminating at the critical points and thestability boundaries of these phases, the spinodals. Depending on themutual disposition of the elements of the stable and metastable T–Pdiagrams, two additional lines of metastable equilibria between the crystallinehigh-pressure phase and each of the metastable disordered phases can appear.These lines terminate at the points of intersection with spinodals. These specialpoints are denoted as pseudo-critical points. A combined analysis of the stableand metastable diagrams gives a reasonable interpretation of the experimentaldata on the phase transformations and on the nature of the anomalous propertiesof the substances in question as well as allowing prediction of some new effects.