Theoretical Study Of Mechanism For Atom Or Molecular Adsorption And Dissociation On Transition Metal Surface

The dynamics of gas-solid surface interaction is arousing more and more interest in the community of chemists and physicists. Whether colloid catalyzed interaction or multi-phase catalysis is relating to the interaction 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 work.The main content in this paper is as follows:Chapter 1: the significance, status 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 dissertation are introduced in detail.Chapter 2: N-Ru system and O-Ag system are studied by using 5-parameter Morse potential (5-MP) method.Chapter 3: The characteristics of adsorption sites and state for NO molecule on Ru low-index surfaces and CO-Pd (211),(311)stepped surfaces 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.This paper has been published on Chemical Research in Chinese University, 2009, Vol.25, No.5, 705⁷10.2. O-Ag system. we dealt with the O-Ag(100),(110),(111) plane surface systems comprehensively, using the 5-MP method, which make it possible for people to understand this important system detailedly and completely. With regard to the adsorption of O atom on the Ag (111) surface, our calculation results suggest that the abnormally low vibration of 27.3, 30meV of EELS experimental results should be resulted by the effect of the sparse steps to the nearest neighbouring hollow site on the Ag (111) terrace. The investigation to O atom adsorbed on the Ag (211), (997), (410) step surfaces also gained better calculation results.3. N-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 are 1732cm^-1,1587 cm^-1,1451(1459) cm^-1å’Œ672 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.4. For the adsorption systems of CO on Pd stepped surfaces, We study mainly CO-Pd(211) and CO-Pd(311) systems. The results show: there exist common characters of CO molecule adsorption on these two surfaces. At low coverage, CO molecule will perpendicularly adsorb in three-fold hollow site of the (111) terrace and has a tilt angle with respect to the surface normal. The critical characters inherit the characters of CO molecule adsorbed in three-fold hollow site of (111) original surface. When the coverage is increasing, two-fold bridge sites of (100) step are occupied. The critical characters inherit the characters of CO molecule adsorbed in two-fold bridge sites of (100) original surface. Considering the different length of (111) terrace, there exist some different characteristics of (211) and (311) stepped surfaces. A number of new sites are exposed on the boundary regions between the two types of surface, for example H5 of (211)and H4 of (311) surface. When the coverage is up, CO will inside in H5 of (211) surface, but the H4 of (311) surface will not be a stable adsorption state.