Structural electronic and vibrational properties analysis of Li2CaX (X = Sn, Pb) heusler alloys: a comparative study

This study was focused on structural, electronic and vibrational properties of Li2CaSn and Li2CaPb with density functional theory. All properties of these compounds were computed by implementing General Gradient Approximation and using Quantum Espresso software programme. As a result of the calculations, it was found that the lattice parameter is 6.967 angstrom and bulk modulus is 33.94 GPa for Li2CaSn. Also, these values are 7.062 angstrom and 29.574 GPa for Li2CaPb. The calculated lattice parameters are in good agreement with the available experimental data. There is no previous theoretical calculation for Li2CaSn and Li2CaPb compounds. It was calculated that Li2CaSn and Li2CaPb have a semi-metal property. The full phonon dispersion curves of Li2CaSn and Li2CaPb compounds in the Heusler type structure were examined using the linear response method. Under 0 kbar pressure, Li2CaPb was unstable while Li2CaSn was dynamically stable. Calculations showed that when 38.42 kbar pressure is applied to the Li2CaPb compound, the Li2CaPb compound becomes dynamically stable. It is believed that this study will shape future studies.