X-Ray Measurement of Order in Single Crystals of Cu3Au

Abstract

X‐ray diffraction methods have been used to measure long‐ and short‐range order parameters for single crystals of the alloy Cu₃Au held at elevated temperatures. It is shown that short‐range order parameters may be obtained by a three‐dimensional Fourier analysis of the ``scattering power'' for the diffuse background scattering of x‐rays, expressed as a function of reciprocal lattice coordinates. Appropriate experimental and computational procedures are outlined. Intensity measurements have been made with a special arrangement of a bent‐crystal monochromator and a Geiger‐counter spectrometer. Short‐range parameters are given for the first ten shells of atoms surrounding a given atom for three temperatures above the critical temperature of Cu₃Au. These results, and those for the long‐range order parameter agree well with theoretical predictions.