[en] The spherical solid model and the spin-density functional formalism have been applied to calculate the screening of a positive point charge at different lattice sites in Al, Na and Cu. Results are obtained for the Knight shift, the electric field gradient, the heat of solution and the diffusion barrier. It is found essential to use the spin-polarized form to evaluate the Knight shift, especially at low metallic densities and for impurities with a high nuclear charge. Both the Knight shift and the electric field gradient are found to be markedly different for substitutional and interstitial positions. The calculated heat of solution of hydrogen is lowest for the octahedral position in fccAl and for the tetrahedral position in bcc Na, indicating that no hydrogen trapping at vacancies occurs in these metals. (author)

[en] The spherical solid model and the spin density functional formalism have been applied to calculate the screening of a positive point charge at different lattice sites in Al, Na and Cu. Results are obtained for the Knight shift, the electric field gradient, the heat of solution and the diffusion barrier. It is found essential to use the spin-polarised form to evaluate the Knight shift, especially at low metallic densities and for impurities with a high nuclear charge. Both the Knight shift and the electric field gradient are found to be markedly different for substitutional and interstitial positions. The calculated heat of solution of hydrogen is lowest for the octahedral position in FCC Al and for the tetrahedral position in BCC Na, indicating that no hydrogen trapping at vacancies occurs in these metals. (author)

[en] To describe the interaction of the two-level systems (TLSs) of an amorphous solid with arbitrary strain fields, we introduce a generalization of the standard interaction Hamiltonian. In this model, the interaction strength depends on the orientation of the TLS with respect to the strain field through a 6 x 6 symmetric tensor of deformation potential parameters [R]. Taking into account the isotropy of the amorphous solid, we deduce that [R] has only two independent parameters. We show how these two parameters can be calculated from experimental data, and we prove that for any amorphous bulk material, the average coupling of TLSs with longitudinal phonons is always stronger than the average coupling with transversal phonons (in standard notations, γ_l > γ_t)

[en] Anisotropic impurity-induced scattering rates and their orbital averages (Dingle temperatures) are expressed in terms of a set of coefficients determined by the band structure of the pure host, and phase shift parameters describing the scattering from a specific impurity. We have evaluated the former set of coefficients in a previous multiple-plane-wave based calculation for dilute Al-Li. The calculation of Li-induced phase shifts was a self-consistent one based on the density functional formalism, but neglected lattice backscattering effects. In order to include the latter we use the so-called Friedel phase shifts obtained from a KKR Green's function calculation, together with the previously calculated host band structure coefficients in a mixed ab-initio calculation of the Dingle temperatures. The agreement with experiment is improved considerably. The effects of alternative refinements to our previous calculation (e.g. the inclusion of nonlocal exchange and correlation) are discussed briefly; they were not found to resolve the discrepancy. We conclude that even a relatively free-electron-like host such as aluminum can produce significant lattice backscattering if the impurity is a strong scatterer of conduction electrons

[en] The self-consistent density functional approach has been applied to a study of electronic properties of vacancies and vacancy clusters in simple metals. The electron density profiles and potentials have been obtained for spherical voids of varying size. The formation energies and residual resistivities have been calculated for vacancies using both the perturbational and variational inclusion of discrete lattice effects. The relation of the void properties to the plane surface properties is studied, and the inadequacy of the jellium-based methods to high-index faces is demonstrated. (author)

No abstract available

[en] The Hueckel model is used to study the electronic structure of monovalent metal cluster. In an fcc cluster the Hueckel model gives an estimate to the electronic structure of a free electron cluster. It is shown that the surface faceting of the fcc cluster can destroy the electronic shell structure already when the cluster has about 100 electrons. In the Hueckel model the icosahedral structure has smaller total energy than the fcc structures, from which the Wulff construction has the smallest energy already when the cluster has 600 atoms. (orig.)

[en] We report molecular dynamics simulations of the impact of TiD clusters on TiD targets. In each cluster collision the total fusion probability seems to be due to a single deuterium collision. The kinetic energies of incident deuterium atoms gradually level off around the initial cluster energy, but do not reach the high energy tail of a corresponding Maxwell-Boltzmann distribution. Neither any other support for a thermonuclear fusion mechanism was observed. On the contrary, our simulations imply that the enhanced fusion rate is rather due to channeled many atom collision cascade type mechanism. (orig.)

[en] The rate of positron detrapping in thermal equilibrium from lattice defects has been calculated by relating it to the specific trapping rate. The results for vacancies, dislocations and surfaces each show a different temperature dependence for the escape rate. For vacancies a measure of the importance of the detrapping can be obtained from the ratio of the vacancy formation energy to the positron binding energy in the defect. The positronium desorption rate from a surface is also calculated and agreement with experimental results is found. (author)

[en] Using the spin-density functional formalism, we have studied the hyperfine fields at interstitial and substitutional impurities in ferromagnetic Ni systematically as a function of the outer-electron configuration and atomic number of the impurities. The core as well as scattering electron contributions to the impurity hyperfine fields are calculated fully selfconsistently. The parameters describing the host electronic structure are obtained from first principle band structure calculations. The results for the systematics in the hyperfine fields are in satisfactory agreement with experiment. (orig.)