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Optimization Methods

The first of the relax subgenus deals with the type of optimization to be performed:

 optimization options for RELAX
 option | status | description : optimization refers to
 int    |    F   | INTERNAL coordinates
 crt    |    F   | CARTESIAN coordinates
 bas    |    F   | BASIS SET exponents/scale factors
 glb    |    F   | GLOBAL scaling factor
 use <opt> for enabling, -<opt> for disabling option <opt>

You can choose between a geometry optimization in the space of internal coordinates (in this case you will need definitions of internal coordinates, of course) or in the space of Cartesian coordinates (these possibilities are mutually exclusive, of course). Furthermore optimizations of basis set parameters (exponents, contraction coefficients and scaling factors) or of a global scaling factor is possible (these options are also exclusive, but can be performed simultaneous to a geometry optimization). For the geometry optimization you should normally use internal coordinates as they provide better convergence characteristics in most cases.