Benzene and Its Dissociation Products on Ir{100}

Abstract

Benzene forms a disorded overlayer when adsorbed on unreconstructed Ir{100} at low temperatures, but is known to dissociate yielding an ordered c(2 × 4) benzyne overlayer at moderate temperatures. Predosing the surface with a low coverage of atomic carbon, however, causes the benzyne overlayer to adopt a c(4 × 4) pattern instead. Here, we investigate the structure and energetics of these overlayers by means of density functional theory calculations, rationalizing the thermodynamic imperatives that drive the transitions between these various phases.

Computational study of the adsorption of benzene and hydrogen on palladium–iridium nanoalloys

“…The adsorption energies reported for the Ir(100) and Pd(100) surfaces are À2.88 eV and À2.03 eV, respectively [35,36]. These are considerably larger (in absolute values) than the corresponding (111) values and explain the preference for the (100) site on the TO [37].…”

Aromatic adsorption on metals via first-principles density functional theory

“…By far, the highest adsorption energy reported for benzene on any transition metal substrate, however, is the value of 2.88 eV calculated recently by Yamagishi et al (2008) for adsorption on Ir{100}. Here, the molecule adopts a flat-lying geometry, centred over the hollow site in an assumed c(4 × 4) arrangement, with two of its C−C bonds oriented along one of the 001 directions.…”

“…When coadsorbed in a c(4 × 4) arrangement with C, calculations show that the presence of adatoms in neighbouring hollow sites forces benzyne to adopt a fully upright geometry, in which the π orbitals of the aromatic ring make a negligible contribution to the binding (Yamagishi et al 2008).…”

“…tilt angle 48 • ) and analysis of the electronic structure demonstrated that adsorbate-substrate binding was due in part to σ bonds involving the dehydrogenated C atoms, and in part due to bonding through the π orbitals of the aromatic ring. When coadsorbed in a c(4 × 4) arrangement with C, calculations show that the presence of adatoms in neighbouring hollow sites forces benzyne to adopt a fully upright geometry, in which the π orbitals of the aromatic ring make a negligible contribution to the binding (Yamagishi et al 2008).…”