|Quantum Chemistry Laboratory|
|Prof. N. Rösch|
The aim of a geometry optimization is to find a stationary point, often a local minimum but also a saddle point (transition state) on the energy hypersurface. Atom-atom distances, bond angles, and dihedral angles are changed by the quantum chemistry program until a stationary point is reached or, more precisely, the stopping criterium is fulfilled.
In this exercise a Z-matrix for formaldehyde shall be constructed which enforces preservation of symmetry during geometry optimization. The Z-matrix of Exercise 1 is not able to do that because each structural parameter is varied independently. It is not sufficient that the symmetry conditions are fulfilled at the beginning of the optimization process since rounding errors may destroy symmetry later on.
To preserve C2v symmetry
As in that exercise, you may correct your entries if you discover a mistake. The solution obtained below is one of several correct alternatives.
|||K. Takagi and T. Oka, "Millimeter wave spectrum of formaldehyde", J. Phys. Soc. Japan, 18 (1963) 1174.|
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