Study of the chemical dependence of the effective pair potentials of Co-Pt alloy

Effective pair interaction potentials of Co-Pt alloy have been obtained from X-ray diffuse scattering measurements on short-range ordered Co₃Pt and Co₆₅Pt₃₅ single crystals. The present work presents the evolution of the interaction energies in the Co-Pt alloy when the Pt concentration varies from 25 to 35 at. %. The aim of this work was to provide data in order to improve the computation of the phase diagram by allowing a concentration dependence of the effective pair potentials. Different methods have been proposed for separating the contributions of local order and first-order displacements from the total diffuse intensity. A comparison of different methods of analysis of Co₃Pt diffuse-scattering intensity data is reported in the Appendix of this article; it shows that the second-order displacement terms are almost zero near the transition temperature.