Force-constant weighted redundant coordinates in molecular geometry optimizations

A novel procedure to select internal coordinates for molecular geometry optimizations is presented. The procedure has features in common with other so-called redundant internal coordinates schemes. It is a black-box method which automatically selects an appropriate set of internal coordinates in which the geometry optimization is performed. The method is explicitly expressed in the non-redundant parameter space, thus avoiding the need for projections from the redundant internal coordinate space. The new procedure introduces a weighting in which the redundancy is modified prior to the generation of the non-redundant internal coordinates. The new method favors those redundant internal coordinates which are the most significant. It has favorable properties for the automatic generation of molecular coordinates in van der Waals complexes and transition state optimizations.