On the importance of the concentration fluctuations correlation function for liquid alloys

In this paper we review the importance of the concentration-fluctuations correlation function Scc for the description of thermodynamic properties of liquid alloys. Using this function we discuss a number of simple phase diagrams and derive some general relations between slopes of phase boundaries at constant temperature or composition. Interchange energies in the Flory model for the systems Rb-Tl, Cs-Tl and Cs-Na are derived using the slope of the liquids of the phase diagram. We conclude that for an accurate description of the liquidus the composition dependence of the interchange energies should be taken into account. In a final section the composition gradients due to external fields (gravity or temperature gradients) are discussed. It is shown that such gradients may strongly affect the outcome of experimental determinations of the thermopower of liquid alloys near the critical point of phase separation