The elastic constants of the L12-type ordered nickel-based intermetallics Ni3X (X = Mn, Al, Ga, Si, Ge), have been calculated by means of ab initio total-energy electronic structurecalculations based on the full-potential linear-muffin-tin-orbital (FLMTO) method. Theorigins in the electronic structure of the variation of the elastic constants, bulk and shearmoduli are investigated across the series, and the effects of the anisotropy of bonding chargedensity on the shear anisotropy factor and the degree of ductility is discussed.

Titanium carbosulfide (Ti2CS) is frequently found as an inclusion phase in Ti - containing steels. It is of considerable interest because, whenever present in preference to the more common manganese sulfide (MnS), it significantly improves the toughness (a very desirable property) of the steel. Currently, to the best of our knowledge, there is no data, either computational or experimental, regarding the structural properties of Ti2CS. This data is needed to understand the influence of the Ti2CS inclusions on the toughness of the host material.

In this paper, our results from the ab-initio calculations, using the LKKR-ASA (Layer Korringa Kohn Rostoker method in the Atomic Spheres Approximation) on the equilibrium ground state properties of bulk Ti2CS are presented and discussed. In particular, attention is focused upon (a) the Energy – Atomic Volume curve generated to calculate the equilibrium lattice constant and the bulk modulus, and (b) the density of states calculations. The application of these results to the subsequent study of an interface involving the carbosulfide and the host matrix is also illustrated.

The electronic structure and bonding character of intermetallic alloys are investigated by a combination of electron energy loss spectroscopy (EELS) experiments and ab initio electronic structure calculations. A detailed comparison is made between experimental spectra and calculations. The changes in electronic structure within a transition metal alurninide series and also due to alloying are studied using EELS spectra. The Korringa-Kohn-Rostoker coherent-potential-approximation method and large supercell models are used to investigate changes in composition and the effect of dopants on the electronic structure.

We investigate the onset and growth of the neck between amorphous Si3N4 nanoclusters at zero and finite pressures. Local stress fluctuations and atomic self-diffusion in the interface region are found to be responsible for neck formation. External pressure has a dramatic influence on the rate of sintering.

The monocyclic and bicyclic ring geometries of C20 are optimized using both the local density functional approximation (LDA) and gradient-corrected density functional theory (BLYP). The energy of the bicyclic ring is found to be higher than that of the monocyclic ring in both LDA and BLYP calculations. The BLYP results confirm the previous single point calculation based on Hartree-Fock geometries[1], which is in favor of the monocyclic ring geometry, while the LDA results still favor the cage geometry. LDA frequencies of both ring geometries are also presented.

The locally self-consistent multiple scattering method is applied to ab initio spin-polarized local density approximation calculations for ferromagnetic CuNi alloys. The samples used to model the alloys are constructed with experimentally measured short range order parameters. These large cell calculations are performed using the Intel Paragon XP/S massively parallel processing supercomputer. The neutron magnetic diffuse scattering cross sections are calculated and compared with experiment. The dependence of magnetic moment formation on the local environment is discussed.

The sputtering probabilities for normal and oblique cluster ion impacts were calculated by the use of two-dimensional molecular dynamics (MD) calculations. These simulations have revealed the angular dependence of ejecting surface atoms on the cluster incidence angle. The ejecting flux has a symmetrical form with an essential lateral component in the case of normal cluster incidence. For an oblique cluster indidence we found a sharp asymmetry of sputtering orientation. We obtained that the ejecting flux consists of three components: a) fast flying atoms with the velocities higher than the cluster velocity ν ∼ 2.3ν0, b) approximately self-similar component with ν ≈ ν0, and, finally, c) slowly moving tail with ν ≈ 0.2ν0, where ν0 is the cluster velocity. According to our MD results we developed a new model of surface modification phenomena which consists of the Langevin Dynamics based on the Kardar-Parisi-Zhang equation, combined with a Monte-Carlo procedure for crater formation at normal and oblique cluster impacts. We obtained that for a symmetrical crater shape with a size in the order of 20 Å, a significant smoothing occurs after irradiation by ∼ 103 cluster impacts which has been supported by experiment at dose of ∼ 1014 ion/cm2. The rate of the smoothing process can be significantly accelerated if the lateral sputtering phenemenon is taken into account. Simulation of oblique cluster impact on a surface at a grazing angle of 30° by constructing of asymmetric crater shape gives an opposite result: the surface roughness increases. The latter obtaining qualitatively agrees with the experiment.

We have carried out molecular dynamics simulations for Xe atoms absorbed in two different zeolites, NaA and AlPO-11. The main emphasis is in the distribution of Xe in the zeolites, Xe-Xen, interactions in NaA, and structural data on Xe-zeolite cage interactions. We report single-particle and pair correlation data, along with diffusion constants of Xe at 300 K. NMR chemical shifts of Xe were estimated using ab initio parametrization.