Co2CrAl Heuslerene: Mechanical, Thermodynamic and Electronic Properties

This work investigates the ground state's stability of the bulk and three Heuslerene Co2CrAl compounds, named as alpha, beta, and gamma phases, by density functional theory (DFT) with the generalized gradient approximation (GGA), GGA+U, and GGA+U+mBJ approximations. The results demonstrate the ground state stability of all mentioned cases since they pass the thermodynamic, elastic, and phonon stability tests. All three structures are more stable in the ferromagnetic phase than the antiferromagnetic phase. In the beta phase, Young's and Shear's moduli were 73.97 GPa and 24.83 GPa, respectively. The thermodynamic diagram has shown existence of the accessible region, which indicates the possibility of making this structure. For all three structures, the phonon branches in the symmetry paths are positive, which represent the complete dynamic stability of these compositions in the presence of mechanical stresses and thermal vibrations. According to the electronic calculations, the bulk phase of Co2CrAl is a half-metal with 3 mu(B) magnetic moment and 100% spin polarization at the Fermi level. Furthermore, all imposed approximations approve that alpha and gamma Heuslerenes are metal for both spin directions, while the GGA+U+mBJ approximation indicates that beta phase is a ferromagnetic half-metal of 1 mu(B) magnetic moment. Based on the electron density diagrams, the highest (lowest) amount of electron density is created on the alpha (beta) phase surface.