HYDROGEN ABSTRACTION FROM A DIAMOND SURFACE. AB INITIO QUANTUM CHEMICAL STUDY WITH CONSTRAINED ISOBUTANE AS A MODEL

Abstraction of terminal hydrogens on a diamond {111} surface by atomic hydrogen has been offered as the possible rate-determining elementary step in the mechanism of low-pressure diamond growth by chemical vapor deposition. We use ab initio multiconfiguration self-consistent-field methods to estimate the activation energy for this abstraction reaction. We do this by first computing features of the potential energy surface for hydrogen abstraction from gas-phase isobutane and then computing features of the potential energy surface for this same system imposing constraints that mimic those found in a diamond lattice. Our results therefore support the use in kinetic modeling or molecular dynamics simulations of activation energies taken from analogous gas-phase hydrocarbon reactions with little or no adjustment