Heats of formation of simple perfluorinated carbon compounds

Journal Article · Thu Jun 17 04:00:00 EDT 1999 · Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory

DOI:https://doi.org/10.1021/jp990425b· OSTI ID:682029

Dixon, D A; Feller, D; Sandrone, G ^[1]

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1. Pacific Northwest National Lab., Richland, WA (United States). Environmental Molecular Sciences Lab.

Fluorocarbons play an important role in a wide range of technological materials including refrigerants, etching materials, and polymers such as poly(tetrafluoroethylene). Obtaining reliable heats of formation of fluorine-containing compounds has been hampered by the difficulties of handling molecular fluorine and HF and the lack of, until recently, reliable heats of formation of standards such as NaF. This type of thermodynamic information is needed for process development, environmental impact studies, and in-use behavior models. The heats of formation of CF{sub 3}, its cation and anion, CF{sub 4}, C{sub 2}F{sub 4}, and :CFCF{sub 3} have been calculated at high levels of ab initio molecular orbital theory. Geometries and frequencies were determined, in general, with second-order perturbation theory. Total energies based on coupled cluster calculations with perturbative triples were determined with basis sets up through augmented quadruple-{zeta} in quality and were subsequently extrapolated to the complete one-particle basis set limit, so as to further reduce the basis set truncation error. Due to its importance as a standard, CF{sub 4} was studied with even larger basis sets. Additional improvements in the atomization energy were achieved by applying corrections due to core/valence correlation, scalar relativistic, and atomic spin-orbit effects. Zero-point energies were based on the experimental fundamentals, when available, and harmonic frequencies obtained from MP2/cc-pVTZ calculations. Missing frequencies for :CFCF{sub 3} were calculated at the MP2/DZP level. The calculated heats of formation (kcal/mol) are as follows: {Delta}H{sub f}(CF{sub 4}) = {minus}221.8 {+-} 1.1 vs {minus}221.6 {+-} 0.3 (expt); {Delta}H{sub f}(CF{sub 3}) = {minus}111.9 {+-} 1.0 vs {minus} 111.7 {+-} 1.0 (expt); {Delta}H{sub f}(CF{sub 3}{sup +}) = 98.0 {+-} 1.2 vs 99.8 {+-} 2.8 (expt); {Delta}H{sub f}(CF{sub 3}{sup {minus}}) = {minus}151.9 {+-} 0.7 vs {minus} 154.9 {+-} 1.0 (expt); {Delta}H{sub f}(C{sub 2}F{sub 4}) = {minus}159.8 {+-} 1.5 vs {minus}156.6 {+-} 0.7 (expt); and {Delta}H{sub f}(:CFCF{sub 3}) = {minus}122.6 {+-} 1.5, all at 0 K. These values are used to calculate a variety of bond energies and molecular energetics.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 682029
• Journal Information: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 24 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ATMOSPHERIC CHEMISTRY
FLUORINATED ALIPHATIC HYDROCARBONS
FORMATION HEAT
MOLECULAR ORBITAL METHOD
TEMPERATURE ZERO K
THEORETICAL DATA