Electronic structure calculations were carried out for a series of hydrogen-terminated carbon clusters designed to model the 100- and 111 -diamond surfaces, Cd(100) and Cd(111). The subjects of the calculations were: (1) methyl radical (CH3) adsorption on an activated diamond surface; and (2) hydrogen abstraction from adsorbed methyl via reaction with gas-phase atomic hydrogen. The largest clusters were treated at the MP2/6-31G*//HF6-31G * level of theory. The results of higher level calculations on smaller clusters were used to estimate corrections to the MP2/6-31G *//HF/6-31G* energies. It is concluded that methyl adsorption is 6.8 kcal mol-1 more exothermic on Cd(100) than on Cd(111). Also, the barrier for hydrogen abstraction from methyl adsorbed on Cd(100) is 2.4 kcal mol-1 lower than that for abstraction from methyl adsorbed on the Cd(111) surface. Finally, the abstraction reaction energy is 0.8 kcal mol-1 lower for methyl adsorbed on Cd(100) compared to methyl adsorbed on Cd(111).
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- Quantum mechanics