Constrained optimizations: coordinate types

Restricted optimizations are performed by freezing certain coordinates, by explicitly referring to one and the same geovar identifier for different coordinates, or by using the selected option. In addition, they are implicit in each Linear Transit or IRC run. All restricted optimizations demand that the type of optimization variables (Cartesian or Z-matrix) equal the type of coordinates used in atoms. zcart input under atoms is considered to be Cartesian in this respect.

If this is violated in a Linear Transit calculation the program will abort. If you apply the Frozen option under geovar, while not using the same coordinate type for atoms as for optimization, an error will occur. If you refer to the same geovar identifier for distinct coordinates while the atoms and the optimization types of variables do not match, the program will continue and assume that you only have assigned the same starting values to the pertaining coordinates. No equality constraints will be in effect then during the optimization.