Intermolecular Forces from Interacting Densities

Oakland University, Rochester MI

Investigators

Abstract

Maria Szczesniak-Bryant and Grzegorz Chalasinki from Oakland University are supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry division to develop theoretical and computational methods to study weak, non-covalent interactions. Such interactions between closed-shell atoms and molecules govern a wide spectrum of chemical and physical phenomena from protein structure and self-assembly to the properties of materials and "sparse matter". Computational chemistry increasingly turns to density functional theory (DFT) for a realistic description of these forces. While DFT alone cannot accomplish this goal, the symmetry adapted perturbation theory based on DFT made major inroads toward such a description. Yet perturbation theory, too, has its limitations especially as concerns convergence. The researchers are developing an alternative DFT-based method which is not grounded in perturbation theory and which can provide equally accurate, potentially exact, interaction energies. In the proposed approach the interaction energy is defined as a functional of monomer densities and it can accurately include all the essential components of interaction energy such as electrostatic, exchange, induction, and dispersion. The formalism developed in this project is expandable to large number of interacting subsystems. The PIs intend to further generalize this approach to the open-shell case. The proposed method is derived from the exact definition of supermolecular interaction energy within DFT and, therefore, it can also guide the construction of new exchange-correlation functionals designed for the treatment of intermolecular forces. This project offers students at Oakland University, particularly undergraduates, an opportunity to engage in basic research related to development and testing of new computational methodologies. The proposed activities promote the collaboration between researchers and students from Oakland, a mid-size regional University, and the University of Warsaw, a prime research institution. The proposed program will train graduate students in method development and computer programming - the skills in much demand in today's knowledge-based economy. The computer codes developed as a result of this project will be open-source and available free of charge to a broad community of researchers.