Chemical Bonding and Reactivity in Extended Systems and Molecules

康奈尔大学的Roald Hoffmann在理论和计算化学项目的支持下开展了一项研究，旨在(1)解释离散或扩展分子的电子结构，这些结构在键合中存在难题；(2)对重要分子类别中的化学键形成定性理解，重点关注分子和扩展系统之间的关系。强调有机和无机结构之间的概念桥梁的构建，(3)广泛和定性地看待表面和界面上的反应性问题，(4)预测尚未合成的具有不寻常性质的系统，(5)为应用量子化学设计进一步的分析工具。将采用的方法将是定性（扩展哈克方法）和定量（密度泛函理论）可靠性的量子力学计算，以及用于构建解释的微扰理论装置。结果有望为广泛的化学家、物理学家和材料科学家提供工具，以分析和理解在广泛的离散分子和扩展结构上的定性键、结构和反应性。尽管量子化学的计算设备处于一个可以对中等大小的分子达到预测化学准确度的阶段，但化学学界仍然强烈需要解释和增加理解。这些解释代表了对分子的结构、能量学和反应性负责的因素的可移植的定性计算，也是本研究的目标。这样的计算可以使用对广泛的科学界定性有用的化学概念，如电负性、轨道、静电和空间效应。

Roald Hoffmann of Cornell University is supported by the Theoretical and Computational Chemistry Program to carry out research that aims to (1) explain the electronic structure of molecules, discrete or extended, that present puzzles in bonding, (2) develop a qualitative understanding of the chemical bonding in important classes of molecules, with a focus on relationships between molecular and extended systems, stressing the construction of conceptual bridges between organic and inorganic structures, (3) look broadly and qualitatively at problems of reactivity on surfaces and at interfaces, (4) predict as yet unsynthesized systems with unusual properties, and (5) devise further analytical tools for applied quantum chemistry. The methodology to be employed will be quantum mechanical calculations of both qualitative (extended Huckel method) and quantitative (density functional theory) reliability, as well as the apparatus of perturbation theory for constructing interpretations. Outcomes are expected to provide a wide range of chemists, physicists, and materials scientists with the tools to analyze and understand qualitatively bonding, structure, and reactivity over a wide range of discrete molecules and extended structures. Although the computational apparatus of quantum chemistry is at a stage where it is possible to attain predictive chemical accuracy for medium-sized molecules, there remains a strong need in the chemical community for explanations and increased understanding. These explanations represent a portable, qualitative accounting of the factors responsible for the structure, energetics, and reactivity of molecules, and are the goals of this research. Such accounting can be couched using chemical ideas that are qualitatively useful to the broad scientific community, such as electronegativity, orbitals, electrostatics, and steric effects.