CALCULATION OF THE FREE-ENERGY AND THE PAIR CORRELATION-FUNCTIONS OF DISORDERED BINARY-ALLOYS BY THE METHOD OF COLLECTIVE VARIABLES

The expressions of the free energy and the pair correlation functions for random binary alloys are obtained by means of the method of collective variables. The advantages of a new approach are discussed. The theory is exemplified by numerical calculations of the K - Cs system properties. The calculated phase diagram is in agreement with the results obtained by other authors and with the experimental data. The analysis of the Fourier transform of the binary correlation function shows that the K(c)Cs1-c alloys are similar to ideal solid solutions at high temperatures (T greater-than-or-equal-to 300 K). As the temperature decreases, the deviation from the ideal solution increases. The short-range order parameter at the first coordinate sphere is calculated.