From electron-phonon transport properties to computational discovery of new materials for energy conversion.

We introduce a novel simplified approach for computing electronic transport properties of complex semiconductors and low-dimensional quantum materials, without empirically fitted parameters. Using this method allowed us to discover new thermoelectric alloy compositions with leading performance and stability. The computational approach achieves good accuracy and transferability while greatly reducing complexity and computation cost compared to the existing methods. The first-principles calculations of the electron-phonon coupling demonstrate that the energy dependence of the electron relaxation time varies significantly with chemical composition and carrier concentration, suggesting that it is necessary to go beyond the commonly used approximations to screen and optimize materials' composition, carrier concentration, and microstructure. The new method is verified using high accuracy computations and validated with experimental data before applying it to screen and discover promising compositions in the space of half-Heusler alloys. We discuss the universality of the Wiedemann-Franz law and deviations from it in semiconductors, computing the Lorenz number from first principles.