ANHARMONIC CONTRIBUTION TO THE DEBYE-WALLER FACTOR FOR COPPER, SILVER, AND LEAD

Using high intensity (70 Ci) Ta183 Mössbauer sources, we have measured the elastic scattering fraction values, scrF, and the relative integrated scattering intensities for the (200), (400), (600), and (220) Bragg planes of copper and silver single crystals; and for the (200), (400), and (600) reflections of a lead single crystal. The experiments were done as a function of temperature from 82 K to a high temperature of 1086, 1211, and 507 K for Cu, Ag, and Pb, respectively. The scrF values were found by Mössbauer line-shape studies, and were used to correct the measured integrated intensities for thermal-diffuse scattering, so that accurate Debye-Waller factors (DWFs) could be evaluated. The measured DWFs for Cu, Ag, and Pb each have a significant anharmonic contribution at about 50% of the melting temperature (Tm). Contrary to what Martin and OConnor have reported for copper, we observed no Q4 contribution to the DWF within our experimental errors, which we estimate to be smaller than those reported by Martin and OConnor. © 1995 The American Physical Society.