Structural, electronic, magnetic, elastic, and thermal properties of Co-based equiatomic quaternary Heusler alloys

In this research work, we have predicted the physical properties of CoFeZrGe and CoFeZrSb for the first time by utilizing first principle calculations based on density functional theory. The exchange-correlation potentials are treated within the generalized-gradient approximation of Perdew-Burke and Ernzerhof (GGA-PBE). The investigated equilibrium lattice parameters of CoFeCrSi are in agreement with available theoretical data and for CoFeZrZ(Z = Ge,Sb) are 6.0013 and 6.2546 Å respectively. The calculated magnetic moments are 1.01μ_B/fu, 2μ_B/fu and 1μ_B/fu for CoFeZrZ(Z = Ge, Sb and Si) respectively, and agree with the Slater-Pauling rule, M_t=Z_t-24. The CoFeZrGe, CoFeZrSb and CoFeZrSi composites showed half-metallic behaviour with 100% spin polarization at equilibrium lattice parameters with band gap of 0.43, 0.70 and 0.59 eV for GGA and an improved band gap of 0.86, 1.01 and 1.08 for GGA + U respectively. Elastic properties are also discussed in this paper and it is found that all the materials are mechanically stable and ductile in nature. The CoFeZrSi alloy is found to be stiffer than CoFeZrZ(Z = Ge and Sb) alloys. The Debye temperatures are predicted by using calculated elastic constants. Moreover, the volume heat capacities (C_v) are investigated by utilizing the quasi-harmonic Debye model.