First-principles study of the structural, electronic, magnetic, mechanical, phonon, and thermoelectric properties of the quaternary Heusler alloys CoVTiZ (Z = Ga, In)

Abstract

We present a first-principles investigation of CoVTiZ (Z = Ga, In) quaternary Heusler alloys to assess their potential as spin-gapless semiconductors and evaluate their multifunctional properties. We comprehensively investigate the structural, electronic, magnetic, mechanical, dynamical, and thermoelectric properties of these compounds using density functional theory. Our calculations reveal that both alloys exhibit thermodynamic stability with negative formation energies of − 1.178 eV/f.u. for CoVTiGa and − 0.168 eV/f.u. for CoVTiIn. The calculated energy above the convex hull per atom for both the compounds is approximately 0.1 eV/atom. Band structure and density of states analysis confirm that CoVTiIn exhibits ideal spin-gapless semiconducting behavior, while CoVTiGa demonstrates nearly spin-gapless characteristics. The total magnetic moments of 2.99 \(\mu _B\) and 3.00 \(\mu _B\) are consistent with the Slater–Pauling rule. Mechanical property analysis reveals that both compounds are mechanically stable and ductile, with CoVTiGa showing better hardness (9.43 GPa) and higher Debye temperature (470.0 K). Phonon dispersion calculations confirm dynamical stability with no negative frequencies. Thermoelectric calculations yield promising dimensionless figures of merit (ZT) ranging from 0.8 to 1.0 at elevated temperatures, particularly in n-type doping regions.