Theoretical Studies of C(100) Surface Reconstruction and Reaction with CH2

Abstract

ABSTRACTThe reconstruction of the C(100) surface and its reaction with CH2 are studied by a cluster model at several theoretical levels [1–13]. For the reconstruction ofthe C(100) surface, the calculated surface dimer bond length is found to be very sensitive to the level of theoretical treatment and the spin state. A single-determinant SCF treatment gives a closed-shell singlet state, higher in energy than the triplet state, and with a dimer length of 1.401 Å, 0.279 Å shorter than the triplet. The correct ground state is a singlet, but a multi-determinant wavefunction is required for its description. At the CI level, the surface dimer bond length in the ground state is found to be 1.508 Å and the energy decrease on dimer formation with respect to the ideal C(100)-lxl surface is 2.28 eV per dimer. For the reaction of CH2 with C(100), no barrier is found for the chemisorption of CH2on the surface and the reaction is highly exothermic. The surface is converted from C(100)-2×1 to C( 100)-1×1 upon CH2 chemisorption.