Ab-initio Studies On The Adsorptions Of Small Molecules And Atoms On Be(0001),Nb(110), And Nb(100) Srufaces

Many studies are now being applied to explore the possibilities to use fabricated simple metal structures instead of transition metals, because simple metals are always lighter and cheaper than transition metals. On the other hand, niobium element as a transition metal with4d valence electrons, however, few of catalytical investigations on niobium surfaces have been studied up to now. Actually the study of small molecules and atoms adsorption on simple metal and niobium surfaces is also of great importance in fundamental research and application.In this project, the density functional theory (DFT) is employed by using VASP package to investigate the hydrogen and water adsorption on Be(0001) surface and nitric oxide (NO) adsorption on Nb(110) and Nb(100) surfaces. The atomic geometries, adsorption sites, electronics and dissociations of the molecules and atoms adsorption on the metal surfaces have been elucidated. The essential results and conclusions we have obtained in this work could be outlined as follows:1) We have reported on DFT total-energy calculations for the adsorption of hydrogen on Be(0001) surface. The atomic geometries, adsorption energy, and surface work function of different hydrogen coverages (from0.06to1.33ML) with various surface supercell for this system have been studied.2) We have used the DFT to perform a comparative theoretical study of water monomer, dimer, trimer, and bilayer adsorption on Be(0001) surface. We have also presented a detailed picture of the electronic structure for the adsorptions by using surface work function analysis, partial density of states, and difference electron density. The aim of present work has been to extract insight into the general features of water-simple metal adsorption systems.3) We have studied nitric oxide adsorption and dissociation on the Nb(110) surface by means of DFT and total-energy calculations. The structural, energetic, vibrational and electronic properties of possible adsorbates including NO and atomic N and O have been calculated and discussed. 4) We have investgated nitric oxide adsorption and dissociation on the Nb(100) surface by using the DFT and total-energy calculations. The structural properties, total energies, surface vibrational modes, and surface electronic structures including work function analysis, partial density of states, and difference electron densities have been calculated and discussed. In particular, the detailed pictures of dissociation pathways for NO dissociation on Nb(100) surface have been presented.