The phonon spectra and elastic constants ofPdxFe1−x: an understanding from inter-atomic interactions

Abstract

Understanding the role of the inter-atomic force constants in lattice dynamics ofrandom binary alloys is a challenging problem. Addressing these inter-atomicinteractions accurately is a necessity to obtain an accurate phonon spectrumand to calculate properties from them. Using a combination of ab initio densityfunctional perturbation theory (DFPT) and the itinerant coherent potentialapproximation (ICPA), an analytic, self-consistent method for performing configurationaveraging in random alloys, we model the inter-atomic force constants forPd0.96Fe0.04 and Pd0.9Fe0.1 alloys based upon the ab initio results and intuitive arguments. The calculated phonondispersion curves and elastic constants agree very well with the experimental results.Comparison of our results with those obtained in a model potential scheme isalso done. The modeling of inter-atomic interactions in random alloys and theirroles regarding the phonon-related properties are also discussed in light of theseresults.