Abstract
The chemisorption of hydrogen and hydrocarbon fragments on catalytically active transition metal surfaces has received considerable attention due to the commercial importance of hydrocarbon formation reactions. Methane in particular is a compound of great economic potential because of its abundance in natural gas, and its use as a raw material for polymers and other organic compounds. Experimentally it has been verified that CH 4 can undergo both physisorption and chemisorption on Ni surfaces. The dynamics of the activated dissociative chemisorption of CH 4 on a Ni (1,1,1) surface has recently been studied by Lee et al. using molecular beam techniques coupled with high resolution electron energy loss spectroscopy (EELS). The barrier against dissociative chemisorption of methane on a Ni (1,0,0) surface has been calculated using ab initio CASSCF-MRCCI calculations on a cluster model. The cluster consists of one active surface Ni atom described at the all-electron level, and 12 bulk Ni atoms described by one-electron effective core potentials. The calculations yield an activation energy barrier of 9.6 kcal/mol. At present there is a rather limited and incomplete theoretical understanding of the chemisorptions of methane on metal surfaces. There is a substantial gap between available experimental information and published theoretical results both for the reaction barrier and for the chemisorptions energy.
Published Version
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