Theoretical studies of the adsorption and diffusion processes on W(111) and W(112) surfaces

Abstract The results of theoretical studies related to the adsorption on transition metal surfaces as well as surface diffusion on such substrates will be presented. These studies were based on the DFT ab-initio structural calculations. We have considered the structural and electronic properties of Ti/W(111) adsorption system . based the theoretical results and measurements of photofield emission spectroscopy the model of the growth of Ti on W(111) substrate has been proposed. It was shown that up to the coverage of one physical monolayer the geometry of adsorbed structure repeats the geometrical properties of tungsten substrate. LDOS distributions obtained for the coverages of one, two and three geometrical layers very well correspond with the spectra provided by photofield emission spectroscopy. The detail study of the electronic properties of Ti/W(111) system let us to show that the set of features, which appears in measured spectra just below the Femi level, represents surface resonances localized at the topmost Ti adatoms. We have also considered adsorption and self-diffusion od tungsten adatoms on W(112) substrate. Our theoretical study let us to clarify the mechanism of motion for in-channel tungsten ad-dimers on this surface. The ad-dimer dissociation-association and the length od adatom-adatom interactions have been analysed. It was found that the long-range interaction between tungsten adatoms located in the same channel influences the height and shape of the activation barrier for the diffusion of adatoms.