Chemical Bonding and Reactivity in Extended Systems and Molecules

Cornell University, Ithaca NY

Investigators

Abstract

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.