A Computational Study of Adducts Between Atomic Chlorine and Carbon Dioxide, Carbonyl Sulfide and Carbon Disulfide Page: 4
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that the bond lengths agree satisfactorily with experiment. The C-S distances
calculated at the HF/3-21G(*) level are about 5 pm shorter than at the
HF/3-21G level, and are closer to the experimental values. Also, use of an
atomic basis set with polarization functions yields a slightly improved C-O
distance in COS. The mean absolute error in bond length for the CXY molecules
is 0.9 pm with the 3-21G(*) basis set. In the rest of this study attention is
therefore mainly focused on data obtained with this larger set. The structure
of CO2 is also calculated using a correlated wavefunction, at the MP2/3-21G
level, which yields r(C-0) = 119.6 pm. This is about 4 pm too large, and
together with the HF result brackets the experimental value. Similarly, MP2/3-
21G(*) calculations on COS yield r(C-O) = 119.4 pm, again about 4 pm too
large, and r(C-S) = 157.1 pm, which is about 1 pm greater than the
experimental distance. Inclusion of electron correlation therefore appears to
have little effect on the calculated C-S distance.
There is good accord between the experimental and calculated vibrational
frequencies of CXY molecules, summarized in Table I. Slightly better agreement
is again-obtained with the larger basis set: the data at the HF/3-21G and
3-21G(*) levels have mean absolute errors of 73 and 52 cm~', respectively.
CS structures of C7CXY adducts
Minima located in the potential energy surfaces for the CICXY adducts
show CS symmetry. The HF wavefunction at each apparent minimum is checked to
ensure that it is stable with respect to perturbations in the orbital
symmetries, and is the lowest energy wavefunction at this geometry . The
stability with respect to small changes in the nuclear geometry is also
tested, to ensure that a true energy minimum is located. Geometries for these
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Marshall, Paul. A Computational Study of Adducts Between Atomic Chlorine and Carbon Dioxide, Carbonyl Sulfide and Carbon Disulfide, article, November 15, 1991; [Amsterdam, Netherlands]. (digital.library.unt.edu/ark:/67531/metadc725816/m1/4/: accessed October 20, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.