We present a consistent analytic representation of the two lowest potential energy surfaces for H3 and their nonadiabatic coupling. The surfaces are fits to ab initio calculations published previously by Liu and Siegbahn and also to new ab initio calculations reported here. The analytic representations are especially designed to be valid in the vicinity of the conical intersection of the two lowest surfaces, at geometries important for the H+H2 reaction, and in the van der Waals regions.
We report a new single-valued potential energy surface for the ground state of H 0 2 from the double many-body expansion (DMBE) method. This new surface conforms with the three-body energy of recent ab initio CAS SCF/CCI calculations semiempirically corrected by the DMBE-SEC method and reproduces the most accurate estimates of the experimental dissociation energy, equilibrium geometry, and quadratic force constants for the hydroperoxyl radical. Using this new H 0 2 (DMBE IV) potential energy function, exploratory dynamics calculations of the 0 + OH -O2 + PI reaction have also been carried out by the quasiclassical trajectory method. Thermal rate coefficients are reported for T = 250, 1250, and 2250 K that are shown to be in good agreement with the best reported measurements.
A novel scheme is suggested to construct a global potential energy surface by switching between representations which are optimal for different energy regimes. The idea is illustrated for the electronic ground state of water for which we use as switched functions the many-body expansion potential of Murrell and Carter [J. Chem. Phys. 88, 4887 (1984)] and the polynomial form of Polyansky, Jensen, and Tennyson, [J. Chem. Phys. 101, 7651 (1994)]. By also modifying the former to reproduce the Coulombic behavior at the collapsed molecular limits for vanishingly small interatomic distances and approximately account for the long range forces, the new potential energy surface has been given double many-body expansion quality. The result is a global H2O potential energy surface which has spectroscopic accuracy and may be used for studies of reaction dynamics.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.