Theoretical Studies of Non-Valence Correlation-Bound Anions and of Positron-Molecule Complexes

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Kenneth Jordan, of the University of Pittsburg is supported by an award from the Chemical Theory, Models and Computational Method program in the Chemistry division to develop computational approaches for studying the binding of extra electrons to molecules and clusters of molecules. Moving electrons from one location to another is the key to processes as diverse as photosynthesis, the operation of transistors, and corrosion. In spite of the importance of excess electrons in biology, chemistry, and physics, how they interact with their surroundings is still not well understood. Professor Jordan and coworkers develop and apply new computational methods to accurately characterize interactions between molecules and of molecules with surfaces. The project provides training of young researchers (students and postdoctoral fellows) in the area of computer modeling. The goal of this project is to provide a detailed understanding of the relative importance of electrostatics and long-range correlation effects in the binding of excess electrons and positrons by molecules and clusters. Due to its scalability on highly parallel computer systems and its potential for giving accurate interaction energies, the diffusion Monte Carlo method is being increasingly applied to chemical problems. However, the diffusion Monte Carlo method requires the use of a trial wave function to fix the nodal surface, and little is known about the magnitude of the associated errors. This research project is designed to address this problem, with particular emphasis on establishing the flexibility in the trial functions for accurate prediction of interaction energies of water with polycyclic aromatic hydrocarbons, with the goal of extrapolating to the graphene limit. The projects are ideally suited to provide the participating students and postdoctoral researchers a broad background in theoretical chemistry and computer simulations. This is a skill set that is in high demand in the workforce. Efforts are planned to recruit more undergraduates, especially women and members of underrepresented minorities, into the group.