Using bond-length dependent transferable force constants to predict vibrational entropies in Au-Cu, Au-Pd, and Cu-Pd alloys

Eric J. Wu; Gerbrand Ceder; Axel van de Walle

doi:10.1103/PhysRevB.67.134103

paper

Using bond-length dependent transferable force constants to predict vibrational entropies in Au-Cu, Au-Pd, and Cu-Pd alloys

arXiv:cond-mat/0302109 · doi:10.1103/PhysRevB.67.134103

Abstract

A model is tested to rapidly evaluate the vibrational properties of alloys with site disorder. It is shown that length-dependent transferable force constants exist, and can be used to accurately predict the vibrational entropy of substitutionally ordered and disordered structures in Au-Cu, Au-Pd, and Cu-Pd. For each relevant force constant, a length- dependent function is determined and fitted to force constants obtained from first-principles pseudopotential calculations. We show that these transferable force constants can accurately predict vibrational entropies of L1 $_{2}$ -ordered and disordered phases in Cu $_{3}$ Au, Au $_{3}$ Pd, Pd $_{3}$ Au, Cu $_{3}$ Pd, and Pd $_{3}$ Au. In addition, we calculate the vibrational entropy difference between L1 $_{2}$ -ordered and disordered phases of Au $_{3}$ Cu and Cu $_{3}$ Pt.

9 pages, 6 figures, 3 tables