Half-metallic character and thermoelectric properties of the K2NaRbAs2 double half Heusler alloy

This paper presents an investigation of the properties of the double half Heusler alloy (DHH) K2NaRbAs2. The structural, elastic, electronic, magnetic, and thermoelectric properties of the alloy are studied using the full-potential linearized augmented plane wave method (FP-LAPW) with the generalized gradient GGA approximation, and the GGA + Modified Becke-Johnson (mBJ) correlation potential is used to calculate the band structures and densities of states. The K2NaRbAs2 DHH alloy is derived from the previously studied parent half Heusler alloys KNaAs and KRbAs in their ferromagnetic phase of type I structure (FM-I). Our findings confirm the thermodynamic stability and synthesizability of K2NaRbAs2 in normal conditions. The alloy is shown to be resistant to distortion and able to withstand reversible deformation. The calculated elastic constants indicate that K2NaRbAs2 is mechanically stable, ductile, and anisotropic, as confirmed by 3D representation of its elastic moduli. Furthermore, the total magnetic moment of 2 mu(B) demonstrates its half-metallic behavior, which mainly due to arsenic atoms. Like its parent alloys KNaAs, and KRbAs, the K2NaRbAs2 DHH alloy could be suitable for use in spintronic technology. Additionally, the thermoelectric characteristics of the K2NaRbAs2 DHH alloy are investigated using semi-classical Boltzmann transport theory, based on a smoothed Fourier interpolation of the bands, as implemented in the BoltzTraP package.