Variational calculation of Helmholtz free energies with applications to simple liquid metals and alloys

It is demonstrated how the calculation of the Helmhodtz free energy, F, including the usual high-order pseudopotential perturbation corrections, can be applied to improve the theoretical F significantly so that the mean atomic volume can be determined theoretically with good accuracy, once T is given, for the NFE-like liquid metals and their binary alloys. The bulk modulus and the thermal expansion coefficient for the alkali, Mg and Al metals and the alkali binary alloys in their liquid states in a self-consistent manner and the free energy and heat of mixing for the Na-K and Na-Cs alloys for which the existing theoretical results are still not satisfactory are calculated. Reasonable success is achieved even for the Na-Cs alloys, in which the effects of the valence-electron charge transfer appear to be very important for the mixing properties. (author)