Runtype control and strategy parameters

With the block key geometry you define the runtype and strategy parameters.

GEOMETRY {RunType { RunTypeData}}
 RunType {RunTypeData}
End

RunType

Can be:
- SinglePoint or SP
- GeometryOptimization or GeoOpt or GO
- TransitionState or TS
- IntrinsicReactionCoordinate or IRC
- LinearTransit or LT
- Frequencies or FREQ
If omitted the run type is GeometryOptimization.
If the key geometry is not used at all the run type is SinglePoint.
The run type specification can be given as argument to the geometry key, or in the data block, but not both. For some run types additional data may be given after the run type specification.

RunTypeData

(Optional) further specifications, depending on the run type. See the sections below.

Omission of the geometry key altogether effectuates a SinglePoint calculation. A straightforward optimization, with all features that can be set with geometry at their default values, is activated by supplying the key with an empty block:

GEOMETRY
End

More subkeys are available in the geometry block than just the run type specification. They are used to control strategy parameters such as convergence criteria. All subkeys are optional: default values take effect for those omitted. Some of the subkeys are only meaningful for certain run types. They will be ignored for other run types.

The initial approximation of the Hessian matrix, which may affect the number of optimization steps that are carried out to reach convergence, is not controlled by the key geometry, but by the key HESSDIAG, and/or by the key geovar. See the section Initial Hessian.

The convergence in gemorty optimizations and frequency runs can be improved by smoothing the generation of integration points (implemented in ADF 2004.01), see the section Smoothing of Gradients.