Experimental determination of pair interaction energies in aCoPt3single crystal and phase-diagram calculations

Abstract

The short-range order in a ${\mathrm{CoPt}}_{3}$ single crystal at $1083 \mathrm{K}$ was measured using neutron diffuse scattering in the (100) and (110) reciprocal planes. The data were used in conjunction with the inverse cluster variation method in order to extract the first four and the sixth effective pair interaction energies. The interactions obtained from the experimental short-range order intensities are used to calculate the Pt-rich side of the phase diagram using the cluster variation method, the order-disorder transition temperature at the stoichiometric composition by Monte Carlo simulations, and the unrelaxed antiphase boundary energies. The agreement with experimental data is excellent. Comparison of the ${\mathrm{CoPt}}_{3}$ pair energies with those similarly obtained in ${\mathrm{Co}}_{3}\mathrm{Pt}$ by other authors shows an important dependence of the nearest-neighbor pair interaction with concentration.