Thermal conductivity and diffusion-mediated localization in Fe_{1-x}Cr_{x} Alloys

TL;DR

This paper presents a first-principles calculation of thermal transport in disordered Fe_{1-x}Cr_{x} alloys, revealing how disorder induces vibrational mode localization and affects thermal conductivity across temperatures.

Contribution

It introduces a novel diagrammatic approach combined with a Kubo-Greenwood formula for calculating thermal properties in disordered alloys from first principles.

Findings

Thermal conductivity shows quadratic temperature dependence below 20 K.

At high temperatures, thermal conductivity saturates and becomes temperature-independent.

Disorder causes significant localization of vibrational modes in Fe-Cr alloys.

Abstract

We apply a new Kubo-Greenwood type formula combined with a generalized Feynman diagram- matic technique to report a first principles calculation of the thermal transport properties of disordered Fe_{1-x}Cr_{x} alloys. The diagrammatic approach simplifies the inclusion of disorder-induced scattering effects on the two particle correlation functions and hence renormalizes the heat current operator to calculate configuration averaged lattice thermal conductivity and diffusivity. The thermal conductivity K(T) in the present case shows an approximate quadratic T-dependence in the low temperature regime (T < 20 K), which subsequently rises smoothly to a T-independent saturated value at high T . A numerical estimate of mobility edge from the thermal diffusivity data yields the fraction of localized states. It is concluded that the complex disorder scattering processes, in force-constant dominated disorder alloys such as Fe-Cr, tend to localize the vibrational modes quite significantly.