A new semiconducting full Heusler Li2BeX (X = Si, Ge and Sn): first-principles phonon and Boltzmann calculations

Abstract

The Full Potential-Linearized Augmented Plane Wave (FP-LAPW) is employed into density functional theory (DFT) within WIEN2k package to explore and investigate the thermoelectric, mechanical, electronic and structural properties of full-Heusler alloys Li<inf>2</inf>BeX (X = Si, Ge and Sn) were explored. The exchange and correlation potential are treated by different approximations: the generalized gradient approximation with Perdew-Burke-Ernzerhof scheme (GGA-PBE) and Tran-Blaha modified Becke-Johnson (mBJ-GGA). The results achieved for the electronic properties show that these compounds are semiconductor in nature with an indirect band gap, of values: 0.60 eV, 0.55 eV and 0.24 eV for Li<inf>2</inf>BeSi, Li<inf>2</inf>BeGe and Li<inf>2</inf>BeSn, respectively. In addition, these materials are mechanically stable owing to the fact that the conditions required for this mechanical stability satisfy Born’s criteria, and are of a brittle nature due to the calculated values of the ratios (B/G), on the other hand, these compounds are dynamically stable due to the non-presence of negative frequencies following the detailed study of phonons. These compounds are characterized by a high figure of merit (ZT) (close to unity) and high Seebeck coefficient (S), making them promising candidates for thermoelectric applications. © 2022 Elsevier B.V., All rights reserved.