Discarded gems: Thermoelectric performance of materials with band gap emerging at the hybrid-functional level

Abstract

A finite electronic band gap is a standard filter in high-throughput screening of materials using density functional theory (DFT). However, because of the systematic underestimation of band gaps in standard DFT approximations, a number of compounds may be incorrectly predicted metallic. In a more accurate treatment, such materials may instead appear as low band gap materials and could have good thermoelectric properties if suitable doping is feasible. To explore this possibility, we performed hybrid functional calculations on 1093 cubic materials listed in the Materials Project database with four atoms in the primitive unit cell, spin-neutral ground state, and a formation energy within 0.3 eV of the convex hull. Out of these materials, we identified eight compounds for which a finite band gap emerges. Evaluating electronic and thermal transport properties of these compounds, we found the compositions MgSc2Hg and Li2CaSi to exhibit promising thermoelectric properties. These findings underline the potential of reassessing band gaps and band structures of compounds to identify additional potential thermoelectric materials.

The MatHub‐3d first‐principles repository and the applications on thermoelectrics

“…The first direction is to obtain more accurate electronic structures. Updating electronic structures and electrical transport properties obtained from the generalized gradient approximations with the Perdew–Burke–Ernzerhof [172] to more advanced functionals such as the Heyd–Scuseria–Ernzerhof hybrid functional [173‐174] can enhance the precision of the data in the database [175‐182] . The influence of electron–phonon interactions (EPIs) on the electronic structure, known as electron–phonon renormalization (EPR), [183‐187] encompasses the effect of zero‐point vibration at zero temperature and the thermal vibration at finite temperatures.…”