First-principles investigation of thermoelectric performance in KMnZ (Z = Sn, Pb) half-Heusler alloys.

In this study, we performed an in-depth analysis of the structure stability, elasto-mechanical properties, thermophysical characteristics, and thermoelectric behavior of the KMnZ half-Heusler alloy using density functional theory (DFT) implemented through the WIEN2k simulation package. We examined the structural stability across phase types I, II, and III by optimizing their energy configurations. Our results demonstrate that the compound achieves optimal stability in the spin-polarized state of phase type II. Subsequently, we employ density functional perturbation theory (DFPT) to forecast the dynamic behavior of these structured systems. The electronic band structure analysis, conducted using the local spin density approximation (LDA), Perdew-Burke Generalized Gradient Approximation (PBE-GGA), and Tran-Blaha modified Becke-Johnson (TB-mBJ) schemes, reveals that the Heusler alloy exhibits half-metallic properties. Additionally, the calculated second-order elastic parameters confirm the material's ductile nature. To evaluate the thermodynamic and thermoelectric stability under various temperature and pressure conditions, we utilized the Quasi-Harmonic Debye model. The computed magnetic moment is consistent with the Slater-Pauling rule. These findings indicate that the KMnZ half-Heusler alloy is a promising candidate for applications in spintronics and thermoelectrics.