Novel 1:1 stoichiometric rare-earth HoX (X $$=$$ Pd, Ag and Cd) intermetallic compounds: DFT-based study

Abstract

A systematic investigation on structural, electronic, elastic, mechanical and optical properties of novel 1:1 stoichiometric rare-earth $$\mathrm{HoX}\ (\mathrm{X}=\text {Pd, Ag and Cd})$$ intermetallic compounds has been made via ab-initio density functional theory-based linearized augmented plane wave method as coded in wien2k. An outline of local density approximation and generalized gradient approximation have been employed. Structural optimization established the stable CsCl-type cubic structure of $$\mathrm{HoX}\ (\mathrm{X}=\mathrm{Pd, Ag and Cd})$$ compounds. The determined crystal structure stability, compressibility and fracture strength of compounds are enhanced with X in the order $$\mathrm{HoPd}>\mathrm{HoAg}>\mathrm{HoCd}$$ . The interlacing electron dispersion curves at Fermi-level in band structure and density of states substantiate the metallic nature of compounds. The splitting gap between the lower and upper valence bands monotonously becomes narrower with the substitution of heavier core-element $$(\hbox {Pd}\rightarrow \hbox {Ag}\rightarrow \hbox {Cd})$$ . The mechanical constants i.e., bulk modulus (B), Young’s modulus (E), shear modulus ( $${G}_{\mathrm{H}}$$ ), Pugh’s ratio $$(B/G_{\mathrm{H}})$$ , Poisson’s ratio (v) and anisotropic factor (A) have been calculated to corroborate the mechanical properties of compounds. The cationic nature of Ho-atoms and anionic nature of X-atoms has been evaluated through the effective charge $$(\textit{Q}^{*}$$ ) computations. The observed peaks in the low energy region of optical conductivity spectra attribute the intra-band, while the high energy structures are associated with inter-band transitions in $$\mathrm{HoX}\ (\mathrm{X}=\text {Pd, Ag and Cd})$$ compounds. The bond order calculations demonstrate the highest strength of HoCd compound among the herein studied compounds.