Examples: Optimization and symmetry

Example: Geometry Optimization, including symmetry: Formaldehyde

The data-set for formaldehyde is shown below

FORMALDEHYDE

   AM1 T=600 SYMMETRY
   Formaldehyde, for Demonstration Purposes
   
   O
   C 1.2 1
   H 1.1 1 120 1
   H 1.1 0 120 0 180 0 2 1 3
   
   3 1 4
   3 2 4

The keyword SYMMETRY points to the presence of symmetry data, which follow after the last atom and a blank line.
The symmetry data are to be read as:
reference atom, symmetry function, atom(s) affected.
So 3 1 4 means: transfer, from atom 3, the value of variable 1 (i.e. the bond length), to atom 4.
Variable 2 (on the next line) represents the bond length.

Other symmetry functions are:

3: the dihedral angle
7: dihedral angle varies as 120 degrees plus reference dihedral
9: dihedral angle varies as 180 degrees plus reference dihedral
14: dihedral angle varies as negative of reference dihedral
17: bond angle varies as 180 degrees minus reference bond angle

Only the reference variable is followed by a "1", the derived ones are provided with a "0" flag.

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Last updated on August 13th 1996