First-principles study of strain effect on the thermoelectric properties of LaP and LaAs

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 LaX (X = P, As) by density functional theory (DFT) simulations. We show systematically that a meta-GGA combined with scissor correction can efficiently accurately compute structures on fine DFT $k$-grid, which is necessary converging thermoelectric calculations. also strain engineering effectively improve performance. Under the optimal condition of 2% tensile carrier concentration $n=3\times10^{20}~\textrm{cm}^{-3}$, LaP at temperature 1200 K achieve figure merit $ZT$ value $>2$, enhanced 90% compared unstrained value. With doping engineering, thereby could be promising high-temperature materials.