Thermodynamic, structural and elastic properties of Co3X (X = Ti, Ta, W, V, Al) compounds from first-principles calculations

Through first-principles calculations within the framework of density functional theory, we have computed the electronic structures, mechanical elastic properties and thermodynamic properties of a series of Co-based Co3X (X = Ti, Ta, W, V and Al) intermetallic compounds with the cubic L1(2)-type and hexagonal D0(19)-type structures. The obtained lattice constants and formation energy are in good agreement with available experimental data. In terms of calculated mechanical elastic properties and Poisson's ratio, most of these Co3X compounds are mechanically stable and exhibit a good ductile property. The calculations also have uncovered that the obtained elastic parameters including single-crystal elastic constants and polycrystalline moduli of Co3X compounds hold a linearly increasing trend as the melting point of the metallic element of X rises. Moreover, the quasi-harmonic Debye-Gruneisen approach has been turned out to be valid in describing the temperature-dependent thermodynamic properties including heat capacity, vibrational entropy, and thermal expansion coefficients of Co3X compounds. (C) 2012 Elsevier Ltd. All rights reserved.