F H2 3 FH H Potential Energy Surface: Construction of the Reference Configuration State Function Space and MR-ACPF-2 Results

A new electronic configuration reference space (subsequently used in multi-reference averaged coupled pair functional (MR-ACPF) or multi-reference configuration interaction singles and doubles [MR-CI(SD)] level treatments of electron correlation) is determined using the aug-cc-pVQZ basis set as a step toward constructing a new potential energy surface (PES) for the F H2 3 FH H reaction. We use our new reference space to calculate several chemically important properties (e.g., barriers, exothermicity, van der Waals wells) of the F H2 PES. We obtain nonrelativistic barrier heights of 1.32 kcal/mol 1 (bent) and 1.67 kcal/mol 1 (collinear) that are 0.2–0.3 kcal/ mol 1 lower than those obtained from the current best PES. Our nonrelativistic value for the exothermicity is 32.45 kcal/mol , which is 0.7–1.1 kcal/mol 1 higher than the values obtained from some other PESs and 0.45 kcal/mol 1 higher than the experimental value. The van der Waals wells we find are slightly deeper (0.05 kcal/mol ) than the wells on the other PES. The 1-kcal/mol 1 magnitude of the differences among barrier heights, exothermicities, and well depths, obtained in our work and using the most reliable current PESs suggest that to obtain a three-dimensional (3D) PES for the F H2 3 FH H Correspondence to: J. Simons; e-mail: [email protected]. utah.edu Contract grant sponsor: Office of Basic Energy Sciences in the U. S. Department of Energy. Contract grant sponsor: Petroleum Research Fund of the American Chemical Society. Contract grant number: 35708-AC6. Contract grant sponsor: National Science Foundation. Contract grant numbers: CHE-9982420; CHE-0240387; CCR0086013. International Journal of Quantum Chemistry, Vol 106, 1516–1527 (2006) © 2006 Wiley Periodicals, Inc. accurate to 0.2 kcal/mol , we will have to use even higher-level methods (e.g., explicitly correlated wave functions) and include relativistic corrections. We intend to do so in the next phase of this effort that is currently under way. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem 106: 1516–1527, 2006