Onset of diradical character in small nanosized graphene patches

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作者：

J Wang，DY Zubarev，MR Philpott，S Vukovic，WA Lester，T Cui，Y Kawazoe

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摘要：

A family of small graphene patches,i.e., rectangular polyaromatic hydrocarbons (PAHs), that have both zigzag and armchair edges is investigated to establish their ground state electronic structure. Broken symmetry density functional theory (DFT) and plane wave DFT were used to characterize the onset of diradical characterviarelative energies of open-shell and closed-shell singlet states. The perfect pairing (PP) active space approximation of coupled cluster theory was used to characterize diradical character on the basis of promotion of electrons from occupied to unoccupied molecular orbitals. The role of zigzag and armchair edges in the formation of open-shell singlet states is elucidated. In particular, it is found that elongation of the zigzag edge results in an increase of diradical character whereas elongation of the arm chair edge leads to a decrease of diradical character. Analysis of orbitals from PP calculations suggests that diradical states are formally Mobius aromatic multiconfigurational systems.

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关键词：

Theoretical or Mathematical/ coupled cluster calculations density functional theory graphene nanostructured materials/ diradical character nanosized graphene patches rectangular polyaromatic hydrocarbons armchair edges zigzag edges ground state electronic structure broken symmetry density functional theory plane wave DFT open-shell singlet states closed-shell singlet states perfect pairing active space approximation coupled cluster theory molecular orbitals elongation Mobius aromatic multiconfigurational system C/ A7320D Electron states in low-dimensional structures A7125X Electronic structure of fullerenes and fullerene-related materials intercalation compounds A7115M Density functional theory, local density approximation (condensed matter electronic structure)/ C/el