The investigation of basic physical properties of some AB2 type hard compounds using first principle methods

In this study, some structural, electronic, elastic and thermodynamic properties of MN2 (M = Hf, Ta, W) compounds were calculated by using the generalized gradient (GGA) approximation with ab-initio method based on plane-wave pseudopotentials and density functional theory. For these compounds, the lattice parameters, LDA+U and GGA+U effective on lattice parameters, formation enthalpies, phase transitions, band structures, partial and total density of states (DOS) curves, elastic constants, pressure variations, Zener anisotropy factors, Poisson ratios, Hardness ratio, Young and Shear modulus, Debye and Melting temperatures, sound velocities were calculated. In addition, the pressure and temperature dependence of some thermodynamic properties were also investigated. All this parameters were also invastigated for XO2 (X = Hf, Th, Zr) compounds under DFT +U, besides that optical and vibrational properties were calculated. The obtained results were compared with the available experimental and theoretical data. The results showed that the used method gave the accurate results for studied compounds.Key Words : Ab-initio method, XO2 (X = Hf, Th, Zr), MN2 (M = Hf, Ta, W), Density functional theory, GGA, LDA, Structural, Electronic, Thermodynamic, Elastic Optic, Vibrational, Hardness