Frequencies and Widths of Phonons in Dilute Cr-W Alloys

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Abstract
We have made a detailed study of the effects of force-constant changes on the frequencies and the widths of phonons in random dilute alloys. A nearest-neighbor perturbation model including the changes in the mass and the changes in the central and noncentral force constants has been employed. The theoretical results have been compared with the inelastic neutron scattering experiments recently performed on Cr-W alloys containing different impurity concentrations (0.3, 0.8, 1.6, and 3.0 at.% W). The change in phonon frequency on account of the expansion of the crystal lattice on alloying has been considered to explain the experimental results. Although an over-all good agreement between the low-concentration theory and the experiments has been observed at four different concentrations of tungsten atoms in chromium, there exist some discrepancies in certain frequency regions.