Temperature dependence of specular and non-specular leed beams from Cu 3 Au

Abstract

The temperature dependence of intensities of the prominent diffraction peaks in the specular (00) and one non-specular ( 11 ) beam from the (100) surface of Cu 3Au have been measured in the range of 300 to 673 K. The effective Debye temperature associated with the specular beam appears to increase continuously with energy below 50 eV but varies discontinuously at high energies. For the ( 11 ) beam, which was available only in the higher energy range of 65 to 136 eV, the effective Debye temperature varies discontinuously with energy. Parallel and normal components of the Debye temperature were deduced from the two sets of data from which it appears that the two mean square displacements are approximately equal, compared to the harmonic approximation which indicates a difference of 30 percent. The log of peak intensity versus temperature (Debye plot) deviates from the straight line at 60° below the disordering temperature for all beams and all energies.