Heats of Formation of Xenon Fluorides and the Fluxionality of XeF₆ from High Level Electronic Structure Calculations
Journal Article
·
· Journal of the American Chemical Society
Atomization energies at 0?K and heats of formation at 0?K were obtained for XeF?, XeF?, XeF?, XeF?, XeF??, and XeF? from coupled cluster theory including noniterative, quasi-perturbative triple excitations (CCSD(T)) calculations with new correlation-consistent basis sets for Xe up through aug-cc-pV5Z in some cases. In order to achieve near chemical accuracy (? 1 kcal/mol) in the thermodynamic properties, up to four corrections were added to the estimated complete basis set binding energies based on frozen core coupled cluster theory energies: (1) a correction for core-valence effects, (2) a correction for scalar relativistic effects, (3) a correction for first order atomic spin-orbit effects, and (4), in some cases, a second order spin-orbit correction. Vibrational zero point energies were computed at the coupled cluster level of theory. The structure of XeF6 is difficult to obtain. The C?v and Oh structures for XeF? are essentially degenerate with the Oh structure below the C?v structure by 0.19 kcal/mol at the CCSD(T)/CBS level based on an approximate geometry for the C?v structure. The two structures are probably isoenergetic with the C?v slightly lower. The calculated heats of formation are: ?Hf0 (XeF?) = 255.8, ?Hf0(XeF?) = -66.3, ?Hf0(XeF2) = -23.3, ?Hf0(XeF4) = -42.5, ?Hf0(XeF5?) = -160.6, and ?Hf0(XeF6) = -55.9 kcal/mol. The calculated heats of formation for the neutral XeFn fluorides are higher (less stable) than the experimental values from equilibrium measurements by 2.0, 7.7, and 12.2 kcal/mol for n = 2, 4, and 6 respectively. The calculated values are even higher as compared to the heats of formation from photoionization measurements. The calculated results suggest that the experimental heats of formation need to be revised. The fluxional nature of the stereoactive lone pair in XeF6 is noted.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15020624
- Report Number(s):
- PNNL-SA-43953; 2385; KP1301030
- Journal Information:
- Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 24 Vol. 127
- Country of Publication:
- United States
- Language:
- English
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