A first principle study of structural, elastic, electronic and thermodynamic properties of Half-Heusler compounds; YNiPn (Pn=As, sb, and bi)

Abstract

This article deals with the structural, elastic, thermodynamic, and electronic properties of Half-Heusler compounds; YNiPn (Pn = As, Sb, and Bi). The computations are carried out using the pseudopotential plane-wave method within the generalized gradient approximation (GGA). We have noticed the structural stability in the F-43m phase and lattice constants are well matched with experimental results. The elastic, thermodynamic, and major electronic properties are reported for the first time in these compounds. We have derived the bulk, shear, and Young's moduli of elasticity from the knowledge of elastic constants along with the discussion of mechanical stability and strength of YNiPn. The Cauchy pressure and Pugh's ratio emphasizes ductile nature. From the knowledge of elastic properties, it is observed that the Debye temperature and sound velocities are decreasing from As to Bi. The electronic properties are discussed in terms of band profile, the density of states (DOS), charge density plot, and Fermi surfaces. The electronic band structure and DOS clarify that YNiPn compounds are indirect narrow bandgap semiconductors. The origins of the bandgap in these compounds are interpreted. The charge density plot projects the strong covalent bonding between Ni and Pn atoms while an ionic bonding between Y and Pn atoms. The thermodynamic variables like cell volume, bulk modulus, specific heat, Debye temperature, entropy, Grüneisen parameter, and thermal expansion coefficients have also been analyzed under high pressure and temperature as they are of great technological importance. These compounds are found as potential candidates for thermoelectric materials.