The Surface Atomic Diffusion Of Hydrogen On The Graphite Surface Work Function Influence

In the first part of the thesis, by using Stillinger-Weber potential, we carried out the constant temperature molecular dynamics simulations of Si(001) surface structures at different temperatures and single Si adatom diffusing on Si(001) surface or single-layer Si(001) steps at the temperatures ranging 1000K to 1300K.As for the simulations of Si(001) surface structures , our results show that dimers rearranged into p(2×1) cell are the primary structure of Si(001) surface. Besides this, trimers and c(2×2) metastable structures are observed on the surface at different temperature as well as two-dangling-bond single atoms. Up to the surface melting temperature, these metastable structures disappear and the simple p(2×1) structure remains on the surface. About the simulations of single Si adatom diffusing on Si(001) surface or single-layer Si(001) steps at the temperatures ranging 1000K to 1300K, we have presented one new diffusion pathway of single Si adatom diffusing on the Si(001) along the direction perpendicular to dimer rows, that can weaken the diffusion anisotropy. We have investigated the process of single Si adatom diffusing across single-layer Si(001) steps as well and given adatom diffusion pathways of step-flow and transformation of single-layer into double-layer steps. Our results show that the exchange between an adatom and a surface atom plays an important role in the adtom diffusion process above 1000K.In the second part of the thesis, we performed first principles calculations based on density functional theory (DFT) about Hydrogen adsorptions on different sites on Graphite(0001) at different coverage. Calculation results indicate that top and bridge sites on Graphite(0001) are more stable chemisorption. Moreover, little Hydrogen adsorbed on it (0.125coverage) can more lower the work function of the Graphite(0001) surface.