APPROXIMATION OF THE FREE-ENERGY CHANGE ON CRYSTALLIZATION

Approximations of the Gibbs free energy change for crystallization of an undercooled liquid. ΔG, are discussed and compared. When liquid heat capacity data are available, ΔG can be approximated to various degrees of accuracy depending on the completeness of the data. In the absence of these data, it is necessary to make further approximations. It is shown that Turnbull's [4] simple linear approximation for ΔG is generally applicable to pure metals. A new expression is proposed for use with easy glass forming alloys such as Au81.4Si18.6. An approximation due to Hoffman [1] is not appropriate for use with metals and alloys but is adequate for use with organic substances, such as ortho-terphenyl. © 1979.