Equilibrium vacancies and properties of metals at high temperatures

The strong nonlinear increase of high-temperature specific heat and thermal expansivity of metals can be explained by formation of equilibrium vacancies in crystal lattice. Accepting this hypothesis, one gets vacancy concentrations at melting points of the order of 0.1 % in low-melting metals and of the order of 1% in metals with high melting points. For this reason, many authors believe the phenomenon to be of a different nature, e.g., anharmonicity. Important arguments supporting high vacancy concentrations have appeared during the last decade. The relaxation phenomenon in specific heat caused by equilibration of vacancies was observed in tungsten and platinum. New data from differential-dilatometry measurements on copper yielded vacancy concentrations about four times larger than reported earlier. At last, thermodynamical relations favoring high defect concentrations were found.