Multiple scattering theory for supported nanoscale metal chains

The ability to construct low-dimensional nanostructures of magnetic materials opens up a wide variety of interesting physical effects and applications. Until recently few studies have considered systems with one-dimensional periodicity. Recent progress in fabricating monatomic chains of atoms on surfaces provides the motivation for theoretical calculations on such systems. In this thesis the layer multiple scattering method for performing electronic structure calculations on surfaces and interfaces is extended to allow for the treatment of systems with one-dimensional periodicity. A solution of the Poisson equation for a system with one-dimensional periodicity is developed. This involves one-dimensional lattice sums, the evaluation of which has necessitated the derivation of a Ewald sum technique for one-dimensional lattices. Comparison of the one-dimensional solution for arrays of chains to existing two-dimensional solutions confirms its accuracy. Self-consistent electronic structure calculations for 3d chains on the Cu(001) surface have been performed for a variety of chain configurations, including single and multiple chains on the surface, embedded chains and step-edge type chains Quantities calculated include local densities of states, total charges and magnetic moments. Results obtained are consistent with monolayer calculations using the layer multiple scattering method, and also with monolayer and adatom calculations in the literature. The behaviour of the magnetic moments for the chain systems have been interpreted within a simple Stoner-like itinerant magnetism model. Trends in the moments across the 3d series, and between the various systems, are understood in terms of the interaction between states, with hybridisation between the d-orbitals of the 3d chain atoms themselves, and between the d-orbitals of the 3d chain atoms and the sp-orbitals of the Cu substrate, the principal mechanisms. (author)