摘要:
In this thesis the structural, elastic, mechanical, magnetic, electronic, thermodynamic and thermoelectric properties as well as the bonding nature and cohesive energies of the cubic intermetallics, R-Au (R= Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) and the structural, magnetic, elastic and mechanical characteristics of the orthorhombic compounds, R-Au 2 (R= La, Ce, Pr and Eu) have been investigated by using the full potential linearized augmented plane wave (FP-LAPW) method in the outline of the density functional theory (DFT). The structural properties of the cubic R-Au compounds are calculated by PBE and PBEsol potentials. The computed lattice constants are found consistent with the experimental results. Our results show a decreasing trend in lattice constants from Ce to Lu with the exception of the Yb that its divalency confirms. The elastic constants of these compounds are calculated. The Cubic-elastic software and PBE-sol exchange correlation are used to determine the elastic properties of the cubic R-Au intermetallics. The mechanical properties of the compounds like Young modulus, Bulk modulus, Poisson ratio, Anisotropy, Shear modulus, Kleinman parameters, Lame's coefficient, Cauchy pressure and B/G ratio are computed. The positive values of the Cauchy pressure reveal that the bonding nature in these compounds is predominantly metallic/ ionic. Furthermore, the large values of the B 0 /G ratio for these compounds show their ductile nature and the most ductile is CeAu with the highest B 0 /G value of 2.82. The Poisson's ratio shows that these compounds are less compressible and the deviation from unity of the isotropic ratio reveals that they are anisotropic except DyAu and NdAu. The sound velocities for shear and longitudinal waves and Debye temperature are also investigated on the basis of the mechanical properties of R-Au intermetallics. The electronic and magnetic properties of the cubic R-Au intermetallics are calculated by applying Generalized Gradie