Revealing the trend of structural, electronic, mechanical and vibrational properties in Co2VX (X= Si, Ge, Sn)

We report systematic first-principles calculations on the series of Cobalt based full-Heuslers Co2VX (X = Si, Ge, Sn) highlighting the role of X (X = Si, Ge, Sn) atom in determining the strength of hybridization of d-orbitals and ultimately influencing half-metallic character. The effect of Hubbard potential (U) for transition elements of Co and V has been included demonstrating half-metallic ferromagnetism. It has been found that three of them are likely to exhibit the Cu2MnAl phase instead of Hg2CuTi phase, well in accordance with Site Preference Rule. The computed elastic constants validate Born-Haung stability criteria for all of them, affirming the mechanical stability while the mechanical parameters uncover ductile, isotropic and non-directional metallic bonding nature. The obtained positive phonon frequencies establish dynamical stability for three of them. The electronic properties explain the hybridisation of d-orbitals responsible for half-metallicity with narrow band gaps of 1.162 eV, 0.545 eV and 0.493 eV for Co2VSi, Co2VGe and Co2VSn respectively in minority spin channel. The magnetic moments of Co and V are coupled with different strengths in parallel direction indicating ferromagnetic order with total magnetic moment per formula unit obeying Slater Pauling rule of 24. The current DFT based application would further create scope of experimental work to explore their technological applications.

Automated summary

This study conducted systematic first-principles calculations on the Cobalt based full-Heuslers Co2VX, highlighting the influence of X atom on determining the strength of hybridization of d-orbitals and ultimately affecting the half-metallic character. The inclusion of Hubbard potential demonstrated half-metallic ferromagnetism, and the three compounds are likely to exhibit the Cu2MnAl phase instead of the Hg2CuTi phase, as supported by the Site Preference Rule. The mechanical stability and bonding nature were confirmed through computed elastic constants and mechanical parameters, with positive phonon frequencies establishing dynamical stability.