Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 125, Issue 20, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.2378766
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Funding
- Natural Environment Research Council [NE/D001552/1, NER/A/S/2003/00480] Funding Source: researchfish
- Science and Technology Facilities Council [PP/D001269/1] Funding Source: researchfish
- NERC [NE/D001552/1] Funding Source: UKRI
- STFC [PP/D001269/1] Funding Source: UKRI
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The high accuracy ab initio adiabatic potential energy surfaces (PESs) of the ground electronic state of the water molecule, determined originally by Polyansky [Science 299, 539 (2003)] and called CVRQD, are extended and carefully characterized and analyzed. The CVRQD potential energy surfaces are obtained from extrapolation to the complete basis set of nearly full configuration interaction valence-only electronic structure computations, augmented by core, relativistic, quantum electrodynamics, and diagonal Born-Oppenheimer corrections. We also report ab initio calculations of several quantities characterizing the CVRQD PESs, including equilibrium and vibrationally averaged (0 K) structures, harmonic and anharmonic force fields, harmonic vibrational frequencies, vibrational fundamentals, and zero-point energies. They can be considered as the best ab initio estimates of these quantities available today. Results of first-principles computations on the rovibrational energy levels of several isotopologues of the water molecule are also presented, based on the CVRQD PESs and the use of variational nuclear motion calculations employing an exact kinetic energy operator given in orthogonal internal coordinates. The variational nuclear motion calculations also include a simplified treatment of nonadiabatic effects. This sophisticated procedure to compute rovibrational energy levels reproduces all the known rovibrational levels of the water isotopologues considered, (H2O)-O-16, (H2O)-O-17, (H2O)-O-18, and (D2O)-O-16, to better than 1 cm(-1) on average. Finally, prospects for further improvement of the ground-state adiabatic ab initio PESs of water are discussed. (c) 2006 American Institute of Physics.
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