Predictions on structural, electronic, magnetic and thermal properties of new Heusler alloys Cr$$_{{{2}}}$$NbSi$$_{{1-x}}$$Ge$$_{{x }}$$ from first-principles calculations

Abstract

In this study, by using full-potential linearised augmented plane wave (FP-LAPW) method with the generalised gradient approximation (GGA) based on density functional theory (DFT), the structural, electronic, elastic and magnetic properties of the Heusler alloys Cr $$_{\mathrm {2}}$$ NbSi $$_{{1-x}}$$ Ge $$_{x}$$ have been evaluated. The AlCu $$_{\mathrm {2}}$$ Mnl-type structure is more stable than the CuHg $$_{\mathrm {2}}$$ Ti-type structure at equilibrium volume for the compounds. The ground-state properties of our alloys including the lattice parameter and bulk modulus were calculated. In view of Poisson’s and Pugh’s ratio, the ductility and brittleness of Cr $$_{\mathrm {2}}$$ NbSi $$_{{1-x}}$$ Ge $$_{x}$$ has been analysed. The mechanical stability is maintained throughout the pressure range with high value of Debye temperature. The electronic band structures and density of states of our compounds show a half metallic character with total magnetic moments, −3.00 $${\mu }_{\mathrm {B}}$$ per formula unit with indirect band gap, $$E_\mathrm{g}$$ $$=$$ 0.152 eV and 0.262 eV for Cr $$_{\mathrm {2}}$$ NbSi and Cr $$_{\mathrm {2}}$$ NbGe respectively. Furthermore, we have analysed the thermal properties by the quasi-harmonic Debye model. Through the obtained results, we can say that these compounds can be strong candidates for future spintronic applications.