Electronic Structure of Organic Materials: Extremely Short Intermolecular Contacts

乔治城大学的Miklos Kertesz获得了化学部理论、模型和计算方法项目的奖励，他对芳香族和杂芳香族自由基进行了理论和计算研究，这些自由基在分子间表现出非常短的范德华键，在1.7到2.9埃之间。这些短接触引起人们的兴趣有两个原因：-短键对于增强分子物种之间的重叠和电导率至关重要；如果能设计出比范德华分离紧密得多的分子，材料的新特性可能会出现。化学键是物理科学的核心概念：这些极短的接触是化学键吗？是什么影响了它们，它们能不能比现在观测到的更短？为了研究这些系统，Kertesz和同事应用并评估了各种基于密度泛函（DFT）的方法。他们正在将Langreth及其同事开发的一种新的范德华斯密度泛函（vdW-DFT）扩展为一种不受自旋限制的形式主义。他们还采用混合元GGA泛函，经验补充DFT和波函数方法。具有短分子间范德华键的材料与经典有机化合物有很大的不同。它们表现出异常的电、磁和光学特性，可以在技术上加以利用。该项目的最终目标是设计一种具有不同寻常金属性能的新型有机材料。这项工作是由材料研究部凝聚态物质和材料理论项目共同资助的。

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.