We present global ground-state potential energy surfaces for the quintet and singlet spin states of the O4 system that are suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in electronically adiabatic, spin-conserving O2-O2 collisions. The surfaces are based on MS-CASPT2/maug-cc-pVTZ electronic structure calculations with scaled external correlation. The active space has 16 electrons in 12 orbitals. The calculations cover nine kinds of geometrical arrangements corresponding to dissociative diatom-diatom collisions of O2, geometries corresponding to O3-O, geometries identified by running trajectories, and geometries along linear synchronous transit paths. The global ground-state potential energy surfaces were obtained by a many-body approach with an accurate O-O pairwise interaction and a fit of the many-body interaction to 12 684 electronic structure data points for the singlet and 10 543 electronic structure data points for the quintet. The many-body fit is based on permutationally invariant polynomials in terms of bond-order functions of the six interatomic distances; the bond-order functions are mixed exponential-Gaussian functions.
Bibliographical noteFunding Information:
Computational resources were provided by the University of Minnesota Supercomputing Institute, by the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory of Pacific Northwest National Laboratory sponsored by the U.S. Department of Energy, and by the Department of Aerospace Engineering and Mechanics at University of Minnesota. This work was supported in part by the Air Force Office of Scientific Research under Grant No. FA9550-16-1-0161. J. D. Bender was supported in this work by the U.S. Department of Energy Computational Science Graduate Fellowship (DOE CSGF) under Grant No. DE-FG02-97ER25308.
© 2017 Author(s).