First-Principles Study of Strain Effect on Thermoelectric Properties of LaP and LaAs

TL;DR

This study uses density functional theory to explore how strain affects the thermoelectric properties of LaP and LaAs, revealing that strain can significantly enhance their efficiency at high temperatures.

Contribution

It demonstrates that strain engineering combined with advanced DFT methods can optimize thermoelectric performance in lanthanum monopnictides.

Findings

LaP achieves ZT > 2 at 1200 K under 2% tensile strain.

Strain increases thermoelectric efficiency by approximately 90%.

Meta-GGA with scissor correction accurately predicts electronic structures for thermoelectric calculations.

Abstract

Rare-earth monopnictides have attracted much attention due to their unusual electronic and topological properties for potential device applications. Here, we study rock-salt structured lanthanum monopnictides LaX (X = P, As) by density functional theory (DFT) simulations. We show systematically that a meta-GGA functional combined with scissor correction can efficiently and accurately compute electronic structures on a fine DFT $k$-grid, which is necessary for converging thermoelectric calculations. We also show that strain engineering can effectively improve thermoelectric performance. Under the optimal condition of 2% tensile strain and carrier concentration $n=3\times10^{20}~\textrm{cm}^{-3}$, LaP at temperature 1200 K can achieve a figure of merit $ZT$ value $>2$, which is enhanced by 90% compared to the unstrained value. With carrier doping and strain engineering, lanthanum monopnictides thereby could be promising high-temperature thermoelectric materials.