Investigation of structural, electronic and lattice dynamical properties of YMgNi4H4 cubic and orthorhombic for hydrogen storage applications

Abstract

This work presents the results obtained from ab initio calculations based on Density Functional Theory (DFT), to study the compound YMgNi4H4 in two phases cubic and orthorhombic, two methods were used: Full Potential Linearize Augmented Plane Waves (FP-LAPW) and Plane Waves Pseudo Potential (PW-PP). The obtained structural properties agree well with previous works. The cohesive energy, hydrating enthalpy and the formation enthalpy are negative for both structures, our results predict that the orthorhombic phase is the most stable. The calculated band structure indicates that this material has metallic behavior. The elastic constants were calculated using the Density Functional Perturbation Theory (DFPT) formalism. The two structures are mechanically stable based on their values, and other mechanical properties such as the bulk modulus, Young's modulus, shear modulus, Poisson's coefficient were calculated using these elastic constants. By analyzing the elastic anisotropy, this material has a pronounced anisotropy. Using the DFPT, the dispersion of the phonons has been calculated for the two phases, it indicates the stability of these two phases because we notice the absence of imaginary modes. Finally, in the [0, 1540] K° range, the variations of thermodynamic properties as a function of temperature were measured.