Thermodynamic theory of metastable states

Metastability is a very frequent phenomenon in Mechanics, Physics, Materials Science, Chemistry, and Biology. To formulate general thermodynamic theory of metastable states the Gibbs free energy of a system with entropy and pressure as thermodynamic variables was introduced in¹. This approach allows calculating the explicit dependence of the Gibbs free energy on temperature, to calculate the heat capacity, the thermodynamic barrier, dividing metastable and more stable states, and the thermal expansion coefficient. Regarded approach allows also considering the problem of thermodynamic stability under mechanical loading. The problem of influence of the heating/cooling rate on the measured dynamic heat capacity is also resolved in the regarded theory. A phase shift of the temperature oscillations of an ac heated sample is shown to be determined by the relaxation time of the relaxation of the metastable non-equilibrium state back to the metastable equilibrium one. This dependence allows calculating the relaxation time, using experimental data. A general description of the metastable phase equilibrium is included in the regarded theory. Metastable states in AB₃ alloys are also investigated. Reasons for the change from the diffusional mechanism of the supercritical nuclear growth to the martensitic one as the heating rate increases are analyzed as well. The Ostwald stage rule is explained in the regarded theory. Complete general formulation of the thermodynamic theory of metastable states was published, in particular, in². This paper is freely available for everybody on the tutorial site of MIT “The net advance of physics”³. In³ there is also a link to the paper “Metastability” from Wikipedia.

1. Yu. V. Kornyushin, Metallofizika, 1985, 7, No 6, p. 109.

2. Y. Kornyushin, Facta Universitatis, Series: Physics, Chemistry and Technology, 2005, 3, No 2, p. 115.

3. Y. Kornyushin, http://web.mit.edu/redingtn/www/netadv/Xmetastable.html