Theory of Order for the Copper Gold Alloy System

Abstract

The theory of order and disorder, in the form used by Bragg and Williams, is extended to arbitrary composition of the constituent elements. The work is based upon the nearest neighbor interaction assumption of Bethe and the connection between the Bethe and Bragg‐Williams theory is shown. In order to extend the Bragg‐Williams theory to compositions other than 25 and 50 atomic percent, new definitions of order are developed. The results are presented in terms of phase diagrams and curves showing energy vs. temperature, specific heat vs. temperature and state order vs. temperature. These results are of importance in giving a general picture of the order‐disorder transformation for a wide composition range. They are not in detailed accord with experiment due to the rather idealized picture underlying the nearest neighbor assumption.