Predicting the Proton Affinities of H2O and NH3

Journal Article · Wed Apr 01 04:00:00 EST 1998 · Journal of Physical Chemistry A

DOI:https://doi.org/10.1021/jp971510r· OSTI ID:1543391

Peterson, Kirk A. ^[1]; Xantheas, Sotiris S. ^[2]; Dixon, David A. ^[2]; Dunning, Thomas H. ^[2]

---

1. Washington State University Tri-Cities
2. BATTELLE (PACIFIC NW LAB)

High-level ab initio molecular orbital theory has been used to predict the proton affinities of H2O and NH3 at the CCSD(T) level with correlation-consistent basis sets through augmented quintuple-? for the former and augmented quadruple-? for the latter. Diffuse functions have been shown to yield faster convergence to the complete basis set limit for the prediction of highly accurate proton affinities. For these two systems, core-valence correlation effects are small, 0.13 kcal/mol, and were obtained from calculations with core-valence, correlation-consistent basis sets. The electronic component of the proton affinities are 171.56 kcal/mol for H2O and 211.97 kcal/mol for NH3. The zero-point vibrational corrections were taken from experimental values where available and from scaled theoretical values otherwise. The final proton affinity (PA) values at 298 K are PA(H2O) = 165.1 ± 0.3 kcal/mol and PA(NH3) = 204.1 ± 0.3 kcal/mol as compared to experimental values of PA(H2O) = 166.5 ± 1 kcal/mol and PA(NH3) = 204 ± 1 kcal/mol. The calculated values together with our estimated error limits suggest that the experimental value for H2O is too high by 1.5 kcal/mol.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1543391
• Report Number(s): PNNL-SA-28748
• Journal Information: Journal of Physical Chemistry A, Journal Name: Journal of Physical Chemistry A Journal Issue: 14 Vol. 102
• Country of Publication: United States
• Language: English