ANOMALOUS TEMPERATURE-DEPENDENCE OF THE X-RAY DIFFUSE-SCATTERING INTENSITY OF CU3AU

The fine structure of the equilibrium diffuse x-ray scattering of a Cu 3Au(110) crystal reveals an unexpected temperature dependence of the f ourfold peak splitting associated with Fermi surface imaging. The sepa ration of the split diffuse maxima increases with temperature correspo nding to a proliferation of correlated microdomains in a real space pi cture. As current alloy theories based on the calculation of the confi gurational energy do not cover such a temperature dependent microstruc ture, the results of this study outline the importance of the entropy contribution to the alloy free energy.