Electronic Structure of Organic Materials: Extremely Short Intermolecular Contacts

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Miklos Kertesz of Georgetown University is supported by an award from the Theory, Models and Computational Methods program in the Chemistry Division for a theoretical and computational study of aromatic and heteroaromatic radicals that exhibit very intermolecular short van der Waals bonds, in the region between 1.7 to 2.9 angstroms. These short contacts are of interest for two reasons: -Short bonds are essential for enhanced overlap and conductivity between molecular species; new properties might emerge if materials can be designed with molecules that pack significantly more closely than the van der Waals separation. -The chemical bond is a central concept in the physical sciences: are these extremely short contacts bonds? What affects them, and can they be made even shorter than observed until now? To study these systems, Kertesz and coworkers apply and evaluate a a variety of density functional (DFT)-based methods. They are extending a novel van der Waals density functional (vdW-DFT) developed by Langreth and coworkers to a spin-unrestricted formalism. They also employ hybrid meta GGA functionals, empirically supplemented DFT and wave function methods. Materials with short intermolecular van der Waals bonds are very different from classical organic compounds. They exhibit anomalous electrical, magnetic and optical properties that may be exploited technologically. The ultimate goal of this project is to design a new class of organic materials with unusual metallic properties.This work is co-funded by the Condensed Matter and Materials Theory program in the Division of Materials Research.