Lattice thermal conductivity of disordered NiPd and NiPt alloys

TL;DR

This paper presents numerical calculations of lattice thermal conductivity in disordered NiPd and NiPt alloys, analyzing its dependence on frequency, temperature, and composition, and discussing implications for minimum thermal conductivity and mode localization.

Contribution

It extends a theoretical framework for disordered alloys to compute configuration-averaged thermal properties, including detailed dependence on various physical parameters.

Findings

Thermal conductivity varies with frequency, temperature, and alloy composition.

The results support the concept of a minimum thermal conductivity in these alloys.

Numerical estimates indicate the presence of localized and delocalized vibrational modes.

Abstract

Numerical calculations of lattice thermal conductivity are reported for the binary alloys NiPd and NiPt. The present work is a continuation of an earlier paper by us [PRB, 72, 214207 (2005)]which had developed a theoretical framework for the calculation of configuration-averaged lattice thermal conductivity and thermal diffusivity in disordered alloys. The formulation was based on the augmented space theorem combined with a scattering diagram technique. In this paper we shall show dependence of the lattice thermal conductivity on a series of variables like phonon frequency, temperature and alloy composition. The temperature dependence of $\kappa(T)$ and its realtion to the measured thermal conductivity is discussed. The concentration dependence of $\kappa$ appears to justify the notion of a minimum thermal conductivity as discussed by Kittel, Slack and others. We also study the frequency and composition dependence of the thermal diffusivity averaged over modes. A numerical estimate of this quantity gives an idea about the location of mobility edge and the fraction of states in the frequency spectrum which is delocalized.