Empirical potential for methyl-radical association with diamond surfaces

Pascal de Sainte Claire, William L. Hase

Research output: Contribution to journalArticlepeer-review

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An analytical potential-energy function for (Formula presented) association with carbon-atom radical sites on diamond surfaces is derived from experimental energies, structures, and vibrational frequencies, high-level ab initio calculations, and properties of potential-energy functions for (Formula presented), (Formula presented), and (Formula presented) association. This (Formula presented)+diamond potential-energy function is a molecular anharmonic potential written with switching (MAPS) functions and is identified by MAPS/MeDIAM. It is a sum of lattice (Formula presented), nonbonded (Formula presented), and radial site (Formula presented) potential terms. There are many general properties of potential-energy functions for alkyl radical association reactions which are transferable and can be used to help construct (Formula presented). Additional properties of (Formula presented) are determined by ab initio calculations using the restricted and unrestricted quadratic configuration-interaction method, with single, double, and perturbative triple excitations and the (Formula presented) basis set. The MAPS/MeDIAM potential function is used to study (Formula presented) association with a carbon-atom radical site on the diamond (111)\ terrace. The energy for (Formula presented) adsorption with this site is calculated to be 17 kcal/mol lower than the ab initio (Formula presented) bond dissociation energy. A canonical variational transition-state theory calculation, based on the MAPS/MeDIAM potential, gives a value of (Formula presented) for the (Formula presented)diamond (111)\ terrace site association rate constant at 1500 K. A linear free-energy relationship is shown for the kinetics of ⋅H and (Formula presented) association with a diamond (111)\ terrace site.

Original languageEnglish
Pages (from-to)13543-13555
Number of pages13
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number20
StatePublished - 1997


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