Mechanism For Atom,Molecular Adsorption On Transition Metal Surface

The dynamics of gas-solid surface interaction is arousing more and more interest in the community of physicists and chemists. Whether multi-phase catalysis or colloid catalyzed interaction is relating to the interaction between reactants as well as between reactant and catalyzer surface. Therefore, the systemic study on the interaction between atom, molecule and catalyzer surface, especially the interaction with active sites in theory is necessary. Some representative atoms and molecules are selected to study the kinetic behavior of adsorption and diffusion on the flat and defective surfaces by employing five-parameter Morse potential and improved extended LEPS potential in this dissertation. The main content in this paper is as follows:Chapter 1: the significance, status in quo and methods of the investigation in gas-solid surfaces interaction are expatiated. On the other hand the theory methods and cluster modes used in this work are introduced in detail.Chapter 2: N-Ru system, O-Ag(210)system and O,N-Ni(311)system are studied using 5-parameter Morse potential (5-MP) method. Meanwhile, characters of O atom adsorption on different FCC(311) surfaces are summarized.Chapter 3: The characteristics of adsorption site and state for NO molecule on Ru low-index surface and CO on Pt(311) and Rh(311) surface are investigated by extended LEPS method.The main production of this paper:1. N-Ru system. Although the N-Ru system has been studied by many methods, especially experimental methods, only limited information was obtained. There are even more puzzles needed to be explained. For example, a variety of losses were observed for N atom on Ru (1 121) surface, but how to assign these losses? Calculated results demonstrate that the N atom has the tendency to adsorb at three-fold sites. There is no subsurface states for N atom on Ru (1 010) surface and there exist 6 stable adsorption sites for N atom on Ru (1 121) stepped surface which can be classified into 3 types: the on-surface adsorption states, the facet adsorption states and the subsurface states. And other calculated results are in good accord with HREELS experiments. Meanwhile, we predict that there exist some other vibrational frequencies.2. O-Ag(210) system. The O-Ag(210) surface adsorption system is studied using 5-M P method and the 2O-Ag(210) system is investigated by the extended LEPS potential theory to learn the interaction between the adsorption states. Calculated results demonstrate that there are two stable on-surface adsorption sites (B and H) for O atom on Ag(210) surface. There also exist an octahedral subsurface adsorption state with high vibrational frequency and the interaction between the on-surface and subsurface O species is slight. The mode at 54.6 meV, which is close to that observed in HREEL spectra (54-56meV), is assigned to the vibration of O atom on B site under the influence of that on H site.3. N,O-Ni(311) system. For O-Ni(311)system, there are three surface adsorption states and the fcc-3-fold site is metastable due to the competitive adsorption between threefold and fourfold sites. For N-Ni(311) system, however, no surface adsorption state was calculated at fcc-3-fold site because it is completely annihilated due to the competitive adsorption. In addition, subsurface states were predicted and all critical characteristics were obtained for the two systems.4. O-FCC(311) system. Characters of O atom adsorption on different FCC(311) surfaces are compared and summarized. O atom has a trendency to adsorb at high-coordinated sites. According to the different competitive adsorption between threefold and fourfold sites for O atom on different FCC metals, we classify them into 3 types. In addition, the octahedral subsurface state is more stable than the tetrahedral state for O atom on all FCC metals.5. NO-Ru system. The extended LEPS of NO-Ru system are constructed by means of 5-MP. All critical characteristics of the system we obtained, such as adsorption geometry, binding energy, eigenvalues for vibration, etc. are in good agreement with the experimental results. There exist several adsorption states for NO adsorption on Ru(0001) surface:T, B, H and H-B-H sites, and the vibrational frequencies are1754,1565,1455(1463)和549 cm-1 respectively. The unusual vibrational frequency of 1130 cm-1 is atributed to hyponitrite form. For NO adsorption on Ru (1 010) surface, there also exist several adsorption states, but parallel adsorption state is not found.6. CO-Pt(311),Rh(311) system. For CO-Pt(311) system, top (T, T′)site is the most stable state withλ=0, and with coverage increasing, B site can be occupied. On the missing row Pt(311)-(1×2) structure, the characteristics of CO change a little,and CO molecular also adsorb at top(T, T′, T′′) site. Characteristics for the CO-Rh(311) system are similar to that for CO-Pt(311)system.