Accession Number : ADA184237

Title :   Surface Chemistry of Transition Metal Carbides: A Theoretical Analysis.

Descriptive Note : Technical rept.,

Corporate Author : CORNELL UNIV ITHACA NY LAB OF ATOMIC AND SOLID STATE PHYSICS

Personal Author(s) : Jansen,Susan A ; Hoffmann,Roald

PDF Url : ADA184237

Report Date : Jul 1987

Pagination or Media Count : 61

Abstract : Extended Huckel tight binding calculations have been employed to analyze the interactions of oxygen, carbon monoxide and methanol with the (100) and (111) faces of a representative rocksalt carbide, TiC. The (111) face have been experimentally shown to be the most active toward the adsorption, dissociation or decomposition of adsorbates, whereas the (100) face demonstrates very little activity. Calculations suggest that the differential reactivity of the two faces is the result of the coordination of the atom in the active site and the presence of surface carbon. For CO on the (100) the population of the 2Pi* level increases if carbon vacancies are included in the calculations and dissociated occurs. For the (111) metal-terminated face of TiC the population of the 2Pi* level is nearly identical to that calculated for Ti(0001). Methanol dissociates into methoxy and a protic species on the (111) face but remains molecular on the (100). The calculations suggest that the molecular species is stabilized by interaction of the methanolic proton with the surface carbon.

Descriptors :   *CARBIDES, *SURFACE CHEMISTRY, *TRANSITION METALS, INTERACTIONS, OXYGEN, MOLECULES, ROCK SALT, ADSORPTION, CARBON MONOXIDE, ADSORBATES, DECOMPOSITION, CARBINOLS, POPULATION, INTERACTIONS, STABILIZATION, CRYSTAL STRUCTURE, POLYCRYSTALLINE, SURFACE REACTIONS, ISOMERS, CRYSTAL LATTICES, CATALYSTS, ORGANIC COMPOUNDS, TUNGSTEN CARBIDES, DIPOLE MOMENTS, CARBIDES

Subject Categories : Physical Chemistry
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE