Peculiarities of thermodynamic properties of liquid alloys of alkali metals at high temperatures

A program directed toward working out and investigating thermophysical properties of coolants with controlled characteristics for power and technology installations (including energy sources for big orbital stations) has been developed in the Institute for High Temperatures of Russian Academy of Sciences. These coolants are both high temperature and low temperature coolants simultaneously. They are based on two- and three-component alloys of alkali and alkali-earth metals, and have the working range of liquid phase from 200--400 K up to 1,200--1,500 K. Correct thermodynamic description of binary liquid-metal alloys of alkali metals with components Na, K, and Cs in the interval of temperatures from 200--400 K up to 1,200--1,500 K and concentration diapason from 0 up to 1 is the result of this study. The important peculiarity in behavior of thermodynamic functions -- inversion (change of sign) of excessive Gibbs energy of formation Δ bar G*i = RTlnγi and as a consequence of this phenomenon the inversion of excessive entropy -- Δ bar S*i = Δ bar Hi/TRlnγi is discovered. An analogous effect is also displayed in integral excessive functions ΔG* and ΔS* = ΔH/T - ΔG*/T