Alexander Bogicevic

Density-functional bridge between surfaces and interfaces

Interfaces are brought into focus by many materials phenomena, e.g., contacting, materials strength, and wetting. The class of interfaces includes ultra-high-vacuum surfaces, which provide a meeting place for numerous accurate experimental techniques and advanced theory. Such meetings stimulate detailed comparisons on the quantum level between experiment and theory, which develop our theoretical tools and understanding. This creates good positions for broadened applications, e.g., other interfaces, which typically lack adequate experimental tools. Density-functional theory is one key bridge between surfaces and other interfaces. The paper presents some recent typical applications from our group, including brief reports on interface structures (VN/Fe, TiC/Co, TiC/Al 2 O 3 ), dynamic processes at surfaces and interfaces (O 2 /Al(111), scanning-tunneling microscopic spectroscopy and manipulation), adsorption and desorption (CO, N 2 , NO, and O 2 on Al(111)), electronic and magnetic properties at surfaces and interfaces (magnetic effects on TiC/Co, surface state on κ-Al 2 O 3 (001)), and epitaxial growth on surfaces (Al(111) and alike). Similar progress in many worldwide materials groups and networks gives a basis for the ongoing paradigm shift in materials science.

Bridging between micro- and macroscales of materials by mesoscopic models

Abstract The importance of bridging length scales for materials is illustrated by three examples, nematic liquid crystals, strength of materials, and epitaxial growth. Emphasis is on the microscopic scale, with first-principles calculations of molecule–surface interaction, stacking-fault energies, interlayer interactions, diffusion barriers, and adsorbate–adsorbate interactions. Some pilot examples of using such information on the meso- and macroscales with models using director fields, misfit densities of dislocation, and monomer and island densities are presented. The area is predicted to have a great future.

Ultrathin Alumina Films on Metallic Substrates: Structure and Metal Adsorption

First principles density functional calculations are used to study the structure and properties of ultrathin films of alumina on Al(111) and Ru(0001) substrates. We focus on ∼5 A two O-layer films, naturally produced by oxidizing NiAl, Ni 3 Al, and Al deposited on Ru(0001). The interface consists of chemisorbed l×1 oxygen on the underlying metal [1], with a nearly coplanar layer of Al 2 O 3 above. The lowest energy structure of the Al-sublattice is found to consist of zig-zag rows of octahedral and tetrahedral Al ions, resembling the bulk κ-phase. Eleven different adsorbed metals, spanning the periodic table, have been studied [2]. At low coverage the bond is purely ionic; at high coverage most metals bind principally by polarization. Contrary to speculations, isolated vacancies are found on MgO(100) not to directly promote metal nucleation [3], and we suggest this behavior is general. However, ad-OH is found not only to promote island nucleation, but can also, in high concentrations, produce wetting of alumina by Cu [4].