Materials Research Express (Jan 2020)
High temperature and pressure dependent structural and thermophysical properties of Co2VN (N = Sn, Sb) ferromagnetic materials
Abstract
Ab-initio framework investigation of structural stability and thermophysical behavior of two Co-based Heusler alloys is carried out using spin-polarized calculations at high temperature and pressure. The structural characterization in nonmagnetic and ferromagnetic states reveals the ordered ferromagnetic Cu _2 MnAl-prototype structure as stable phase. The optimized lattice constant is found to be consistent with the available experimental value. The continuity in the P–V plot indicates the absence of any structural phase transition from highly symmetric cubic structure to other structural phase. The band structure profile shows perfect half-metallic character with integral 3.00 μ _B magnetic moment for Co _2 VSn and 4.00 μ _B for Co _2 VSb according to the Slater-Pauling rule. Elastic constants convey that these alloys are mechanically stable with a high Debye and melting temperatures. With the incorporation of modified version of Beck-Johnson potential these alloys displays a perfect half-metallic character having an indirect band gap of 1.12 eV and 1.34 eV in spin down orientation of Co _2 VN (N = Sn, Sb) Heuslers respectively. The density of states along with their corresponding band structure delivers the semiconducting nature of alloys in spin down channel for the present set of alloys. Semi-classical Boltzmann theory for heat transport is used to check the applicability of the material for thermoelectric technology. Insight into variation of lattice thermal conductivity shows an exponential decreasing trend for both the compounds intriguing their experimental exploration. Also, a detailed description of thermodynamic behavior of the vital quantities like entropy, thermal expansion, Grüneisen parameter and specific heat were examined using quasi harmonic Debye approximation.
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