An extended Heisenberg model for conjugated hydrocarbons. II. Kekulé basis

Sticking of atomic hydrogen on graphene

Recent years have witnessed an ever growing interest in the interactions between hydrogen atoms and a graphene sheet. Largely motivated by the possibility of modulating the electric, optical and magnetic properties of graphene, a huge number of studies have appeared recently that added to and enlarged earlier investigations on graphite and other carbon materials. In this review we give a glimpse of the many facets of this adsorption process, as they emerged from these studies. The focus is on those issues that have been addressed in detail, under carefully controlled conditions, with an emphasis on the interplay between the adatom structures, their formation dynamics and the electric, magnetic and chemical properties of the carbon sheet.

Clar theory for radical benzenoids

Eric Clar's ideas concerning "aromatic sextets" are extended from closed-shell benzenoids to the case of radical benzenoids, particularly those where the unpaired electrons are largely localized on sites of one "type" (starred or unstarred). A quantitative format in terms of a new Clar polynomial is introduced to make quantitative correlations with a selection of numerical data, including delocalization energies, spin densities, and energy gaps between states of different spin multiplicities. The correlations are generally quite good, thereby further validating Clar's ideas and our extension and quantification of them.