Formaldehyde:
This "pièce de résistance" of all quantum chemical programs
(ESS) is here shown as a result of Kimball's heuristic "spherical cloud"
model. It takes about 2 sec to optimize geometry and obtain the energy
minimum by Silvan Perego's program KIMBALL (diploma thesis, University
of Bern, April 1989). The input is trivially simple. Just choose "EDIT/add
nodes" from a graphical table, add H-atoms automatically, click "CALCULATE/optimize"
and there it goes. You can watch the optimization of the clouds while the
energy minimum is searched. This comes out to be -113.4998 as compared
to Gaussian 94, RHF/STO-3G, -112.3543, and RHF/6-31G(d), -113.8637 hartree
(for the last energy see J.B. Foresman & A. Frisch, Exploring Chemistry
with Electronic Structure Methods, 2nd ed., Gaussian Inc, Pittsburgh, USA
1996, page 17).
Below stereo plot of the final structure. The "p"
clouds are in magenta, above and below the s-skeleton.
Watch their placement nearer to the more electronegative O-atom (a parameter
of the automatic optimization).
An improved set of parameters gives ther following results for Formaldehyde:
Etot
-114.5398868 -V/T
2.0000000
Vnn
31.1032805 Eel -145.6431674
T
114.5398869 V
-229.0797737
Vel
-260.1830542 Vee
69.9219783
Vne
-330.1050325
Formaldehyde
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C-O distance
1.2303 Angstrom (calc.)
C-H distance
1.0792 Angstrom (calc.)
Angle H-C-O
116.9492 degrees (calc.)
Total Energy
-3116.8195 eV (calc.)
Energy of
C-Atom -1030.0800 eV
(exper.)
Energy of
O-Atom -2043.7940 eV
(exper.)
Energy of
2 H-Atoms -27.1960 eV
(exper.)
Total Bond
Energy 363.1907 kcal/mol (calc.)
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