RELATIVISTIC EFFECTS ON GROUND-STATE PROPERTIES OF 4D-TRANSITION AND 5D-TRANSITION METALS

Cohesive energies, bulk moduli and equilibrium lattice constants have been calculated for the 4d and 5d transition metals with face-centred cubic crystal lattices (Rh, Pd, Ag and Ir, Pt, Au). For the total energy calculations according to the density functional theory on the local density approximation the authors have used an ab initio pseudopotential method. Two calculations have been performed for each element using either nonrelativistic or scalar-relativistic ionic pseudopotentials. The pseudo-wavefunctions and charge densities of the valence electrons have been represented by a mixed basis of plane waves and localised orbitals derived from the atomic d pseudo-wavefunctions. For the 5d metals they find a significant improvement of the results by the relativistic treatment, as expected because of their heavy atomic nuclei. In the case of the 4d metals the relativistic results are of similar quality as for the 5d metals, but now the nonrelativistic values are slightly closer to the experiment, possibly due to an error cancellation effect.