Theory Study Of The Adsorption And Dissociation Of H₂O On Li₃PO₄ Surfaces And Propylene Oxide Isomerization On Au Surface

In this dissertation, density function theory has been used to the mechanism of water adsorbed and dissociated on Li3PO4(100), (010), (001) and (110) surfaces, as well as the isomerization of propylene oxide on Au(111) surface. The main contents are as follows:1. The adsorption of water molecule on the different sites of Li3PO4(100), (010), (001) and (110) surfaces has been studied with a periodic slab model by GGA-PBE. Optimized the most stable geometries of water molecule adsorbed on the five ideal surfaces were obtained, and the adsorption energies are -1.149,-1.039,-1.679,-0.677 and-0.760 eV, respectively. The interaction between water molecule and Li3PO4(100) surface is the most strongest. The calculated results indicated that water molecule is inclined to locate on the surface site with its H atom being attracted by the O atom of phosphate ion and its O atom being close to Li ions when we compared different adsorption energies and geometrical parameters. Mulliken population analysis results showed that some electrons transfer from the Li atom of substrate to water molecule.2. The reactions of water molecule dissociation on Li3PO4(100), (010), (001) and (110)-A,B surfaces have been studied by transition state theory. The dissociation reaction: H2Oâ†'H (ads)+OH (ads). OH and H altogether adsorbed on Li3PO4 surfaces was calculated firstly. The results showed that OH tended to be adsorbed on the Li-Li bridge site of the surface by its oxygen atom to surface Li atoms, and H atom tended to be adsorbed on the O site of the surface to form hydroxyl groups. The lowest activation energy of water molecule adsorbed on Li3PO4(100), (010), (001) and (110)-A,B surfaces are 0.752,0.748,1.484,0.242, and 0.231 eV, which indicates that water molecule is easy to dissociate on Li3PO4(110) surface and hard on (001) surface.3. The mechanism of propylene oxide isomerization on Au(111) surface has been studied by with a periodic slab model by GGA-PBE. We first investigated the propylene oxide molecule adsorbed on Au(111) surface. There were two diffirent adsorption configurations, and the configuration by the O atom of propylene oxide absorbed on Au atom top site was more stable. There were four reaction pathways about the isomerization reaction processes of acetone molecule, and the products were allyl alcohol, acetone, propanal, and methyl vinyl ether, respectively. The isomerization of propylene oxide to allyl alcohol, acetone, and propanal contained common change process: â‘  C-H and C-O bonds rupture;â‘¡ H atom shift to Au surface;â‘¢ form intermediate;â‘£ H atom shift to form new C-H bond or C-O bond. The major diffirent of the isomerization of propylene oxide to methyl vinyl ether was the cleavage of C-C bond and not the breaking of C-O bond.