Thermodynamics of stable and metastable equilibria in water in the T-P region

Water is considered as a regular solution of two structural components, their local configurations corresponding to the atomic short-range order of the Ida and hda modifications of amorphous ice. The expression for the Gibbs potential, Delta G(T,P,c), includes four model constants, i.e. the difference of the specific volumes, Delta V-0, entropies, Delta S-0, and energies, Delta E-0, of the Ida and hda components as well as the parameter U characterizing the mixing energy of the components in the binary solution. The concentration c of the hda component is determined from minimizing Delta G with respect to c. The T-P phase diagram calculated on the basis of this model agrees quantitatively with the experimental data and qualitatively with the computer calculations using the method of molecular dynamic simulation (MDS). (C) 1999 Elsevier Science B.V. All rights reserved.