Anti-Wilson mechanism for adjusting bandgap and electronic transport property of a half-Heusler material LiCdP

Abstract Using first-principles calculations, we have found that LiCdP, an existing half-Heusler material, exhibits an anti-Wilson mechanism for adjusting the bandgap. Specifically, instead of widening according to the conventional Wilson mechanism, the bandgap shows a significant decrease in response to lattice strain, eventually closing at 5.02% tensile strain. This anti-Wilson mechanism is attributed to the weakened repulsion between the 3 s and 5 s orbitals of the P and Cd atoms, respectively, as observed by the analysis of the neighbouring atomic orbital coupling. In addition, we have found that the ZT value, which measures the thermoelectric efficiency of this material, can reach 1.33 at a temperature of T = 1200 K when lattice strain is induced by thermal expansion. This result suggests that LiCdP is an excellent thermoelectric material in a high operating temperature range. From the point of view of actual applications, such an interesting tunability of the bandgap of LiCdP provides a novel alternative for designing electronic or optoelectronic devices in a controllable way.