The Theoretical Research On Adsorption And Dissociation Of Gaseous Atom And Molecule On Metal Surface

The dynamics of gas-solid surface interaction is arousing more and more interest in the community of physicists and chemists. Multi-phase catalysis and colloid catalyzed interactions are 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.The main contents in this paper are as follows:Chapter 1: the elementary theory for calculation in this paper and the low-index surface cluster models are given.Chapter 2: the adsorption and diffusion for N-Pt,C-Fe low-index surface systems and , O,N-Ni(311) stepped systems entirely are investigated by constructing atom-solid surface interaction potential named five parameters Morse potential (5-MP for short).Chapter 3: we investigate the characteristic of adsorption and dissociation for CO molecules on Fe surfaces by extended LEPS method.The main production of this paper:1.The adsorption system of N atom on the Pt low-index surfaces. The vibrational frequencies are easy to measure in experiments, and are the most important critical characteritics to ascertain the adsorption sites and states. However, the experiments are carried out under different conditions, and mostly obtain bitty information. Moreover, the problem on the attribution of frequencies is usually inconsistent. Our theoretical results show that N atom can only adsorb in the four-fold hollow site on Pt (100). N atom adsorbed in LB and H3 sites on Pt(110) surface. And affirmed that the loss spectroscopy 390cm-1 observed in experiments corresponded the surface vertical vibration frequency of N atom adsorbed in LB sites. Our calculation results were supported by comparing to experimental and theoretical results of this similar system. Not only recurred the vibration frequency surveyed by experiment, but also affirmed the corresponding adsorbed sites of the conflicting vibration frequency by assigned. This work validated the experimental and theoretical results,and gave reasonable expline.2.The adsorption system of C atom on the Fe low-index surfaces. The experimental studies and corresponding theoretical researches are scarce. The calculation results showed that C atom adsorbed in the four-fold hollow site on Fe(100) surface; on Fe(110) surface,the most stable adsorption sites were quasi-3-fold sites; and excluded the possibility that Erley considered the loss spectroscopy of 360 cm-1 bringed by the rotation of CO molecule on Fe surface. C atom adsorbed in quasi-3-fold sites on Fe(111) surface.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.CO-Fe low-index surfaces system. We investigated CO-Fe(100) system using the extended LEPS of constructed by means of 5-MP (the 5-Parameter Morse potential) in detail. We obtain all critical characteristics of the systems, such as adsorption geometry, binding energy, eigenvalues for vibration, etc. And we analyze the dissociation mechanism of the CO molecule on Fe(100) surface. The calculation results showed that CO molecule firstly adsorbed on the bridge sites, and then adsorbed stably on top sites as CO molecules increasing. On Fe(111) surface , CO firstly adsorbed in hollow sites at low coverage , then adsorbed on top sites as the increasing coverage, and the a1 mode changed to a2 mode which adsorbed in deep hollows. For the system of CO-Fe(110),the adsorption sequence of CO molecule on Fe(110)surface exists dispute in theory, viz. the binding energies sequence of the three adsorption sites was abnormal. We speculate the reason of the abnormal binding energies may be the interaction between molecules with increasing coverage . For the adsorption and dissociation of CO molecule on Fe(100) surface, the calculation results showed on Fe(100) surface, at low coverage, CO molecule adsorbs in four-fold hollow site with unusual low stretching frequency of 1131 cm-1. With increasing coverage, CO molecule adsorbs perpendicularly in sequence in the bridge and top sites with the frequency of 1921cm-1 and 1957 cm-1. Our calculation results support the investigation of three molecular statesα(α1,α2,α3) obtained in experiment definitely. Meanwhile, We analyze the dissociation mechanism of the CO molecule on the surface, and obtain the dissociation trans-state H-B-H, with the dissociation potential barrier of 0.36 eV. The calculation results show that, at low coverage, the adsorption state in four-fold hollow site is a metastable state, viz., the precursor state of dissocation.