Estimations of global warming potentials from computational chemistry calculations for CH 2F 2 and other fluorinated methyl species verified by comparison to experiment

Paul Blowers, Kyle Hollingshead

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

In this work, the global warming potential (GWP) of methylene fluoride (CH 2F 2), or HFC-32, is estimated through computational chemistry methods. We find our computational chemistry approach reproduces well all phenomena important for predicting global warming potentials. Geometries predicted using the B3LYP/ 6-311g** method were in good agreement with experiment, although some other computational methods performed slightly better. Frequencies needed for both partition function calculations in transition-state theory and infrared intensities needed for radiative forcing estimates agreed well with experiment compared to other computational methods. A modified CBS-RAD method used to obtain energies led to superior results to all other previous heat of reaction estimates and most barrier height calculations when the B3LYP/6-311g** optimized geometry was used as the base structure. Use of the small-curvature tunneling correction and a hindered rotor treatment where appropriate led to accurate reaction rate constants and radiative forcing estimates without requiring any experimental data. Atmospheric lifetimes from theory at 277 K were indistinguishable from experimental results, as were the final global warming potentials compared to experiment. This is the first time entirely computational methods have been applied to estimate a global warming potential for a chemical, and we have found the approach to be robust, inexpensive, and accurate compared to prior experimental results. This methodology was subsequently used to estimate GWPs for three additional species [methane (CH 4); fluoromethane (CH 3F), or HFC-41; and fluoroform (CHF 3), or HFC-23], where estimations also compare favorably to experimental values.

Original languageEnglish (US)
Pages (from-to)5942-5950
Number of pages9
JournalJournal of Physical Chemistry A
Volume113
Issue number20
DOIs
StatePublished - May 21 2009

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Computational chemistry
computational chemistry
global warming
Global warming
Computational methods
methylidyne
estimates
radiative forcing
Experiments
Geometry
Methane
Fluorides
Reaction rates
Rate constants
geometry
methylene
Rotors
rotors
fluorides
partitions

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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title = "Estimations of global warming potentials from computational chemistry calculations for CH 2F 2 and other fluorinated methyl species verified by comparison to experiment",
abstract = "In this work, the global warming potential (GWP) of methylene fluoride (CH 2F 2), or HFC-32, is estimated through computational chemistry methods. We find our computational chemistry approach reproduces well all phenomena important for predicting global warming potentials. Geometries predicted using the B3LYP/ 6-311g** method were in good agreement with experiment, although some other computational methods performed slightly better. Frequencies needed for both partition function calculations in transition-state theory and infrared intensities needed for radiative forcing estimates agreed well with experiment compared to other computational methods. A modified CBS-RAD method used to obtain energies led to superior results to all other previous heat of reaction estimates and most barrier height calculations when the B3LYP/6-311g** optimized geometry was used as the base structure. Use of the small-curvature tunneling correction and a hindered rotor treatment where appropriate led to accurate reaction rate constants and radiative forcing estimates without requiring any experimental data. Atmospheric lifetimes from theory at 277 K were indistinguishable from experimental results, as were the final global warming potentials compared to experiment. This is the first time entirely computational methods have been applied to estimate a global warming potential for a chemical, and we have found the approach to be robust, inexpensive, and accurate compared to prior experimental results. This methodology was subsequently used to estimate GWPs for three additional species [methane (CH 4); fluoromethane (CH 3F), or HFC-41; and fluoroform (CHF 3), or HFC-23], where estimations also compare favorably to experimental values.",
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