Formulation of the integral Gibbs energy of crystalline elements versus temperature and mechanical stress

Phase equilibria calculations require the knowledge of the whole Gibbs energy functions referred to standard elements. Nevertheless, in mechanical calculations the relative change in free energy, already formulated by Landau is often used for the description of the elastic energy of a solid. In order to have a better consistency between the two approaches, it is now suggested a formulation of the integral change of the Gibbs energy of a crystal under stress in equilibrium with a surrounding medium by generalizing the definition of the Gibbs energy of an isotropic substance under hydrostatic pressure.