Structural, elastic, mechanical and thermodynamic properties of Terbium oxide: First-principles investigations

摘要

Highlights ? Structural stabilities, elastic, thermodynamic properties of TbO are investigated. ? The RS phase of TbO was found to be mechanically stronger among the cubic structures. ? For hexagonal structures, NiAs phase was found to be stronger than WZ phase of TbO. ? TbO is ductile with ionic bonding for ZB, CsCl and WZ phases. ? TbO is brittle with covalent bonding for RS and NiAs phases. Abstract First-principles investigations of the Terbium oxide TbO are performed on structural, elastic, mechanical and thermodynamic properties. The investigations are accomplished by employing full potential augmented plane wave FP-LAPW method framed within density functional theory DFT as implemented in the WIEN2k package. The exchange-correlation energy functional, a part of the total energy functional, is treated through Perdew Burke Ernzerhof scheme of the Generalized Gradient Approximation PBEGGA. The calculations of the ground state structural parameters, like lattice constants a 0 , bulk moduli B and their pressure derivative B ′ values, are done for the rock-salt RS, zinc-blende ZB, cesium chloride CsCl, wurtzite WZ and nickel arsenide NiAs polymorphs of the TbO compound. The elastic constants (C 11 , C 12 , C 13 , C 33 , and C 44 ) and mechanical properties (Young’s modulus Y, Shear modulus S, Poisson’s ratio σ, Anisotropic ratio A and compressibility β ), were also calculated to comprehend its potential for valuable applications. From our calculations, the RS phase of TbO compound was found strongest one mechanically amongst the studied cubic structures whereas from hexagonal phases, the NiAs type structure was found stronger than WZ phase of the TbO. To analyze the ductility of the different structures of the TbO, Pugh’s rule (B/S H ) and Cauchy pressure ( C 12 – C 44 ) approaches are used. It was found that ZB, CsCl and WZ type structures of the TbO were of ductile nature with the obvious dominance of the ionic bonding while RS and NiAs structures exhibited brittle nature with the covalent bonding dominance. Moreover, Debye temperature was calculated for both cubic and hexagonal structures of TbO in question by averaging the computed sound velocities.