Structural, elastic, mechanical, electronic, magnetic and optical properties of half-Heusler compounds CoFeZ (Z = P, As, Sb): A GGA plus U approximation

The first-principles study technique is implemented to explore Co-based H-H compounds, namely CoFeP, CoFeAs, and CoFeSb. In this study we have investigated the structural, elastic, electronic, magnetic, and optical properties using DFT as a fundamental approach within simulation package WIEN2k, utilizing linearized augmented plane wave method with full potential. Calculations for electronic exchange-correlation energy are performed using GGA (Generalized Gradient Approximation) approach together with the on-site Coulomb interactions effect as (GGA + U). Using Phono3py code, we have calculated the phonon spectrum of CoFeZ compounds and there is no negative frequency in the phonon spectrum which shows the dynamic stability of CoFeZ (Z = P, As, Sb) compounds. Large lattice constants are seen for all three compounds CoFeP, CoFeAs, and CoFeSb. Elastically, the former two compounds CoFeP and CoFeAs are ductile while the latter one, CoFeSb is brittle. All the compounds show small band gaps for spin-down channels hence confirming half-metallic character. It is found that magnetic moments follow the Slater-Pauling 18M(t) = Z(t)-18 electron rule with the high total magnetic moments. Also, optical properties such as refractive index, absorption coefficient, dielectric function, conductivity, and reflectivity are calculated and discussed, which show that all the compounds are highly active at intermediate energy spectra.& nbsp;