X-ray measurement of order in CuAu

Abstract

The long-range order in CuAu has been measured with a Geiger counter spectrometer using filings quenched from various annealing temperatures. The long range order is essentially perfect at low temperature, and decreases to about 0.97 at 380°C, where the material changes to CuAuII. Short-range order coefficients were determined from measurements of the diffuse intensity from a single crystal of CuAu. The coefficients indicate a preference for unlike nearest neighbors, and they are qualitatively similar to those for Cu 3Au. An outward shift of the 100 and 300 diffuse peaks suggests but does not prove the existence of a microlayering, similar to CuAuI, even above the critical temperature.