Theoretical Studies On The Hydrogen Relevant Reaction Mechanisms Of Two Kinds Of Important Molecules

As to some important reactions, people have not been satisfied to stay in the superficial phenomenon. For some important chemical reactions relevent to people's life, they wanted to find out the mechanism of the reaction process, and further to control it, which involves microscopic processes of atoms or molecules. However, as the limitation of the experimental technologies, the interaction mechanism in atomic and molecular level still can't be observed in experiment directly. So, people urgent need some other means to compensate for the lack of experiment. With the Quantum mechanics has been very successful in dealing with the problem of the microscopic systems, such as atoms and molecules etc. It provides tools for analyzing the reaction process theoretically in atomic level. Some micro informations can be obtained by the theoretical method, which is difficult to observe in experiment. The micro informations can be used to reveal the reaction mechnism and explain the experimental phenomena. The current quantum computation method which have been used for dealing with the molecular problem is widely used to study the relationships between the molecular structure and properties and the relationships between the structure and the reaction path, and other aspects now. In this thesis we studied two kinds of important hydrogen relevant reaction mechanisms by applying the quantum computing method. The main contents summarized as follows:1. We investigated the transformation processes from a physisorption state to a chemisormption state of a H2 molecule adsorbed on the solid materials in theory. Physical adsorption and chemical adsorption are two kinds of forms of H2 molecules existed on the solid materials. People pay more attentions on the two kinds of forms, but the transformation processes are less attention. However, this transition process can affect the dynamic stability of hydrogen storage system directly. The DFT-LDA calculations was performed for studying the transformation mechanism from physical adsorption to chemical adsorption of the H2 molecule adsorbed on a pristine C20 and a C19B systems. We first predict the existence of transition state in the transformation process by analyzing the characteristic of MOs. Then we obtained the precisely potential energy surface by fully optimize. And the stationary points and transition states are explored. Our calculate results show that the physisorption energy of H2 molecule adsobed on C20 is smaller than on C19B. For both the two transformation processes of the H2 molecule adsorbed on a pristine C20 and a C19B systems should across one energy barrier, but the energy barrier for the transformation processes from the physisortion state to the chemisorption state is very low, especially for the C19B. The charge transfer between H2 and C19B is the essential reason for the adsorption intensity of H2 and C19B is more bigger. However the charge transfer also brought another problem that the distance of H-H increase because of the mutual exclusion which makes the H-H dissociate easily. It should be the reason that the H2 molecule dissociate on C19B more easily.2. In addition, we summarized four types of molecular form of hydrogen molecule by analyzing the H2 molecule interact with the pure C20 and boron-doped fullerenes C19B and interact with two C19B. One is the free state of hydrogen molecule. The second is the form that hydrogen molecule adsorbed on the pure carbon materials by van der Waals actions. The third is a more complex forms in which the charge transfer between the hydrogen molecule and adsorbed materials surface, so van der Waals and coulomb actions both exsit. The fourth is a form in which the two hydrogen atoms both interac with material by adsorbed materials.3. Condering the practical application we seclet the C59B fullerene which e have been observed in experiment and could be synthesized even in macroscopic quantity and they are stable above room temperature. Due to the high stability and operability of the synthetic maneuverability in experiment, and the adsorption energy is adjust to the hydrogen storage, C59B has ever been regared as an very promising material in hydrogen. The DFT calculations for studying the transformation processes from a physisorption state to a chemisorption state of a H2 molecule adsorbed on C59B system. We predict the existence of transition state in the transformation process by the analyzing the characteristic MOs. The energy barrier is very low for the transformation processes from the state P to the state C. Thus, the C59B·H2(P) has much lower kinetic stability. Therefore, from practical consideration, the material of B-doped fullerene which has ever been regarded as a prospective hydrogen storage material should be reassessed.4. Using the spin-unrestricted density function theory, we investigated the chiral conversion mechanism of thalidomide molecule at B3LYP/6-31+G(d, p) level. We first attained the transformation process of isolated thalidomide molecule without any assistant of other molecule, we obtained two paths of the transformation. The results indicate that one energy barrier of 70 Kcal/mol should be crossed if the thalidomide molecule accomplished the chiral conversion by itself. Such a big energy barrier is contradicted with that the chiral conversion of the thalidomide molecule is very fast. So we should consider the influences of the external environment. The highent energy barrier of the transfer in gas phase is the H transfer. So we introduce two H2O molecules in this step. The energy barrier reduced to about 31.94 Kcal/mol 31.38 Kcal/mol when two H2O molecules are introduced into the two transfer process as the transfer bridge. Thus theoretically illuminates the chiral conversion mechanism of thalidomide molecule, explains why does the chiral conversion occur in solutions.The research results mentioned above have enriched the theoretical basis of the hydrogen storage mechnism of the fullerene materials, and explained the conclusions in experiments of the chiral conversion mechnism of thalidomide molecule.