With this award, the Chemical Structure, Dynamics and Mechanism (CSDM-B) and Computational and Data-Enabled Science and Engineering (CDS&E) programs are supporting computer-based fundamental research of Dr. Charles Doubleday at Columbia University. This research seeks a deeper understanding of the mechanisms of chemical reactions by computing the sequence of atomic motions as starting materials are transformed into products. Dr. Doubleday uses a combination of quantum mechanics and classical mechanics to understand how energy flows from starting materials into products. This type of calculation allows important questions to be addressed; for example, why one product may be favored over another. The understanding achieved in these calculations will enable better experimental control over the products of chemical reactions. An important component of this project is the training of undergraduate students in scientific research. Since research is collaborative and students learn from each other, the work fosters group skills as well as individual achievement. In collaborations with colleagues at Columbia and other institutions, Dr. Doubleday helps train students in the use of computational methods. In one project, the focus is on the active center of a class of powerful antibiotics, with the goal of understanding and control. As the principles uncovered by this research become incorporated into applied areas, potential benefits could include greater understanding and control over chemical processes important in atmospheric and life processes.
The computational procedure involves quasiclassical ab initio molecular dynamics, in which nuclear forces are computed at each step by an electronic structure method, usually density functional theory. In applying this method to several enediyne cyclizations, the Doubleday group has recently found a dynamic isotope effect in which isotopic selectivity occurs in the product, as a result of competition between recrossing to reactant on a vibrational timescale and isotope-dependent intramolecular vibrational redistribution. An important part of the proposal is to carry out quasiclassical simulations of reactions in condensed phase using QM/MM (Quantum Mechanics/Molecular Mechanics) techniques. The proposal describes a statistically converged procedure for quasiclassical sampling of transition states in condensed phase.
