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.