Quantitative analysis of thermal conductivity reversal in binary alloys by an experimentally constrained first-principles calculation framework

The thermal conductivity of pure metals usually decreases with temperature as enhanced electron-phonon scattering while alloys can exhibit a weakly temperature-dependent or even increasing thermal conductivity. Although this behavior has been qualitatively attributed to strong residual resistivity within the framework of Wiedemann-Franz law and Matthiessen's rule, a more comprehensive mechanistic understanding remains elusive. In this work, we integrate density functional theory, semiclassical Boltzmann transport theory and experimental electrical resistivity data to investigate the opposite temperature dependence of thermal conductivity in three high-thermal-conductivity alloy systems (W Re, Cu Zn, and Au Ag). Results indicate that alloying systematically suppresses both the electrical and thermal transport kernels by modifying electronic states near the Fermi level while the experimentally constrained effective relaxation time becomes less temperature-dependent. The reversal occurs when the positive temperature dependence of the thermal-transport kernel is no longer overcompensated by the temperature-induced decrease in the relaxation time. This work establishes a quantitative framework for separating the electronic-structure and scattering contributions to thermal transport in alloy systems.