Hybrid Directionality and Bond-Bending Analysis (BEND)
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Reference
J. P. Foster and F. Weinhold, J. Am. Chem. Soc. 102, 7211-7218 (1980).
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Notes
NHO Directional Analysis is performed by default ("BEND" keyword is optional). NBO now determines the direction(s) of all spndm hybrids, including d-rich hybrids at transition metal centers. Optional keywords allow selection of threshold angular deviations, percentage non-s character, and occupancy of tabulated hybrids. The direction of each hybrid is specified in terms of the spherical polar angles theta and phi from the nucleus (in the coordinate system of the host program) as well as the deviation angle Dev from the line of centers between the bonded nuclei. The Sample Output illustrates bond-bending for the cyclopropane molecule (RHF/3-21G level), where the carbon skeletal hybrids are conpicuously bent (by ~23 degrees) out of alignment with the edges of the C3 equilateral triangle. (See NBO 6.0 Manual, p. A20 for additional discussion).
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Sample Input (G9X)
#rhf/3-21g pop=nbo
RHF/3-21G for cyclopropane (C3H6)
0 1
C
C 1 1.5122
C 2 1.5122 1 60.0000
H 1 1.0716 2 117.8437 3 107.7570
H 3 1.0716 1 117.8437 2 107.7570
H 2 1.0716 3 117.8437 1 107.7570
H 1 1.0716 2 117.8437 3 252.2430
H 3 1.0716 1 117.8437 2 252.2430
H 2 1.0716 3 117.8437 1 252.2430