First-principles calculations to investigate pressure effects on structural, elastic, electronic, optical and thermodynamic properties of AB2 (A= Hf, Zr, and BCo, W) type laves phases

Abstract

In present investigation, we elucidated the structural, elastic, optical, mechanical, electronic, and thermodynamics properties of AB2 (A = Hf, Zr, and BCo, W) laves phases via first principles scheme of density functional hypothesis. The effect of pressure on various physical aspects up to 100 GPa accounted to this research and found significant changes at different pressures. The results we obtained for the present enquiry have been quantified with the previous research of relevant work and relatively better performance is obtained. The cell parameters as well as unit cell volume are found to be decreased with applied pressure since the interatomic distances of atoms became shorter with pressure. The negative formation enthalpy ensures the chemical and thermodynamical stability of the studied phases. Using Born approximation criterion the mechanical stability has been verified where the phase transition of AB2 (A = Hf, and BCo, W) and AB2 (A = Zr and BCo, W) has been observed after 20 GPa and 40 GPa respectively. It was observed that elastic moduli of AB2 (A = Hf, Zr, and BCo, W) increases with increasing pressure. The higher C11 values among three elastic moduli show higher resistance to linear compression for the current study which is even better than the previously reported result. Mechanical performance has been measured in terms of shear modulus (G), bulk modulus (B), and Young modulus (E) using Vigot-Reuss-Hill method. The estimated data shown pressure rising G, B, and E values indicates dominating stiffness properties under applied stress which ensure their industrial applications. The increased nature of machinable index of all these phases unsure their huge applications in cutting tool geometry, cutting fluids and and plastic strain. The Poisson and Pugh ratio analysis suggests that at zero pressure only the phase HfCo2 shows brittle nature and the other phases AB2 (A = Zr, and BCo, W) show ductile nature from 0 to 100 GPa. The electronic properties investigated through density of state (DOS) calculations revels the metallic characteristics of the titled phases. Decrease in total DOS at high pressure is observed for all the phases. Under pressure it was found that optical indices like absorption coefficient, conductivity, loss function, reflectivity, and dielectric functions are gradually shifted toward higher energies confirming that these materials can be used solar cells to reduce solar heating, and in UV light-based device for high absorption. Higher Debye temperature, thermal conductivity and melting temperature of AB2 (A = Hf, Zr, and BCo, W) are found at ambient condition and these parameters are increasing with increasing pressure which ensure the high temperature industrial applications of these phases. Among four laves phases, relatively higher mechanical, optical, and thermodynamic performance is obtained for HfW2 compound.

Keywords

• DFT simulation
• Structural aspects
• Bulk features
• Bonding properties
• Optical and thermal behavior