Ab initio modeling of metal adhesion on oxide surfaces with defects

Our ab initio studies show that surface defects cause redistribution of the electron density which can increase substantially the binding energy of metal atoms to oxide surfaces. The results for electron (F(0)(s)) and hole (V(0)(s)) centers in the adhesion of Ag atoms (at 1:4 and 1:1 coverages) to a MgO(100) surface, combined with previous studies for charged defects, support earlier ideas of the mechanism of radiation-enhanced adhesion of nonreactive metals on oxide substrates. The results suggest that some optical control of adhesion energies is possible through charge transfer.     

Theory of defects and defect processes

Most studies of imperfect solids concentrate on the properties of individual isolated defects. These include electronic structure, formation energies and diffusion parameters of point defects and point defect aggregates. Many physical phenomena are determined by defect processes, in which defects interact or the defect state of the lattice evolves. Such phenomena include the radiation damage process and subsequent development of microstructure, the matter and charge transport in the growth of oxide films, the recombination—or ionization—assisted diffusion in many systems, and a range of degradation mechanisms. These and other examples are discussed. The emphasis is on those cases where quantitative theory can unravel phenomena which experiment alone cannot easily do, notably those situations where the time scales are inconvenient or the system too complex for easy experimental analysis.     

Lattice dilatation of boron in silicon

Recent data on laser-annealed, boron-implanted silicon are analysed, and the results compared with earlier experiments and simple theory. Each substitutional boron decreases the total volume by about 90% of the volume per silicon atom in the perfect crystal.     

Importance of quantum tunneling in vacancy-hydrogen complexes in diamond

Our ab initio calculations of the hyperfine parameters for negatively charged vacancy-hydrogen and nitrogen-vacancy-hydrogen complexes in diamond compare static defect models and models which account for the quantum tunneling behavior of hydrogen. The static models give rise to hyperfine splittings that are inconsistent with the experimental electron paramagnetic resonance data. In contrast, the hyperfine parameters for the quantum dynamical models are in agreement with the experimental observations. We show that the quantum motion of the proton is crucial to the prediction of symmetry and hyperfine constants for two simple defect centers in diamond. Static a priori methods fail for these systems.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.