REACTION OF CH4 WITH SUBSTITUTIONAL FE NI(111)/

The reaction of CH4 with a substitutional Fe/Ni(111) surface is treate d using a many-electron embedding theory, modelling the lattice as a 4 1-atom, three layer cluster. Ab initio valence orbital configuration i nteraction (multiple parent) calculations carried out on a local surfa ce region permit an accurate description of bonding at the surface. Th e 3d orbitals are explicitly used for the Fe atom and six nearest neig hbor Ni atoms in the local surface region. The calculated activation e nergy for CH4 dissociation at an atop Fe site to produce CH3 and H coa dsorbed on the surface is 5.7 kcal/mol, compared with 16.7 kcal/mol on Ni(111). The reaction of CH4 --> CH3(ads) + H(ads) is predicted to be 4 kcal/mol exothermic on the Fe/Ni(111) surface and the immediate dis sociation products are CH3 and H coadsorbed at across atom three-fold sites. Across bond dissociation is energetically very unfavorable. The bonding properties of coadsorbed CH3 and H on the Fe/Ni(111) surface are similar to those on the Ni(111) surface. Compared to the clean Ni( 111), the substitutional Fe/Ni(111) surface is very effective in activ ating CH4.