Ab initio calculations of vibrational frequencies and infrared intensities for global warning potential of CFC substitutes. CF{sub 3}CH{sub 2}F (HFC-134a)

Journal Article · Thu Mar 16 00:00:00 EST 1995 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100011a006· OSTI ID:35475

Papasavva, S; Tai, S; Esslinger, A; Illinger, K H; Kenny, J E ^[1]

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1. Tufts Univ., Medford, MA (United States)

We have investigated the feasibility of using ab initio molecular orbital methods for predicting the global warming potential of the proposed chlorofluorocarbon (CFC) substitute CF{sub 3}CH{sub 2}F, HFC-134a. Various levels of theory and basis sets were used to optimize geometry and calculate harmonic vibrational frequencies and infrared intensities for the molecule using the GAUSSIAN 92 software package. In attempting to assess the quality of the computations, we found it necessary to reconsider the vibrational assignments available in the literature. On the basis of the current assignment, we find that for the highest level calculation, MP2/6-31G{sup **}, the calculated harmonic frequencies agree extremely well with the experimentally observed ones at frequencies below 800 cm{sup {minus}1}, with a systematic error toward higher calculated frequencies becoming apparent above 800 cm{sup {minus}1}. At lower levels of theory, the systematic error is apparent at all frequencies. The regularity of the deviation between calculated and observed frequencies makes ab initio calculations of vibrational frequencies much more useful than semiempirical calculations, which tend to show random deviations, as demonstrated with a PM3-UHF calculation in this work. The calculated absolute intensities are in good agreement with the limited experimental measurements previously reported. 23 refs., 3 figs., 5 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 35475
• Journal Information: Journal of Physical Chemistry, Vol. 99, Issue 11; Other Information: PBD: 16 Mar 1995
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
66 PHYSICS
99 MATHEMATICS
COMPUTERS
INFORMATION SCIENCE
MANAGEMENT
LAW
MISCELLANEOUS
FLUORINE COMPOUNDS
INFRARED SPECTRA
GREENHOUSE EFFECT
HALOGENATED ALIPHATIC HYDROCARBONS
VIBRATIONAL STATES
FREQUENCY MEASUREMENT
EXPERIMENTAL DATA
NUMERICAL DATA
MOLECULAR ORBITAL METHOD
COMPUTER CALCULATIONS
MOLECULES
GLOBAL ASPECTS