# New Global Potential Energy Surfaces of the ground 3A' and 3A' states of the H2O system

## TL;DR

This paper introduces two highly accurate global potential energy surfaces for the lowest electronic states of the O+H2 system, enabling detailed reaction dynamics studies and improved agreement with experimental data.

## Contribution

The work provides new, precise analytical PESs for the $^3A'$ and $^3A''$ states of O+H2, with better saddle point characterization and long-range behavior, suitable for reaction dynamics simulations.

## Key findings

- New PESs reproduce saddle point features more accurately.
- Quantum and classical dynamics match experimental cross sections.
- Long-range potentials are free of cutoff issues.

## Abstract

This paper presents two new adiabatic, global potential energy surfaces (PESs) for the two lowest $^3A'$ and $^3A''$ electronic states of the O($^3P$)+H$_2$ system. For each of these states, ab initio electronic energies were calculated for more than 5000 geometries using internally contracted multireference configuration interaction methods. The calculated points were then fitted using the ansatz by Aguado et al. [Comput. Phys. Commun. 108, 259 (1998)] leading to very accurate analytical potentials well adapted to perform reaction dynamics studies. Overall, the topographies of both PESs are in good agreement with the benchmark potentials of Rogers et al., but those presented in this work reproduce better the height and degeneracy of the two states at the saddle point. Moreover, the long range potential in the entrance channel does not require any cutoff. These features makes the new PESs particularly suitable for a comparison of the dynamics on each of them. The new set of PESs were then used to perform quantum mechanics and quasiclassical trajectory calculations to determine integral and differential cross sections, which are compared to the experimental measurements by Garton et al. [J. Chem. Phys., 118, 1585 (2003)].