The phonon spectra and elastic constants of Pd(x)Fe(1-x): an understanding from inter-atomic interactions.

Understanding the role of the inter-atomic force constants in lattice dynamics of random binary alloys is a challenging problem. Addressing these inter-atomic interactions accurately is a necessity to obtain an accurate phonon spectrum and to calculate properties from them. Using a combination of ab initio density functional perturbation theory (DFPT) and the itinerant coherent potential approximation (ICPA), an analytic, self-consistent method for performing configuration averaging in random alloys, we model the inter-atomic force constants for Pd(0.96)Fe(0.04) and Pd(0.9)Fe(0.1) alloys based upon the ab initio results and intuitive arguments. The calculated phonon dispersion curves and elastic constants agree very well with the experimental results. Comparison of our results with those obtained in a model potential scheme is also done. The modeling of inter-atomic interactions in random alloys and their roles regarding the phonon-related properties are also discussed in light of these results.