Natural internal coordinates

The redundant optimization scheme [53] can be applied to natural internal coordinates, which are sometimes redundant for polycyclic and cage compounds. It can also be applied directly to the underlying primitives. 

Baker J and Chan F 1996 The location of transition states a comparison of Cartesian, Z-matrix, and natural internal coordinates J. Comput. Chem. 17 888... 

FogarasI G, Zhou X, Taylor P W and Pulay P 1992 The calculation of ab initio molecular geometries efficient optimization by natural Internal coordinates and empirical correction by offset forces J. Am. 

Pye C C and Poirier R A 1998 Graphical approach for defining natural Internal coordinates J. Comput. Chem. 19 504... 

In the original formulation, a set of 3A - 6 independent natural internal coordinates was chosen. It was later discovered that the same optinaization characteristics could be... 

D. Rappoport, Computational photochemistry, in M. OHvucci, (Ed.), Computational and Theoretical Chemistry, Vol. 16, Elsevier, Amsterdam, 2005, Chapter 3 M. Amim, R. Ahlrichs, Geometry optimization in generalized natural internal Coordinates, J. Chem. Phys. Ill (1999) 9183. 

Baker J (1993) Techniques for geometry optimization A comparison of Cartesian and natural internal coordinates. J Comput Chem 14 1085-1100... 

Pye CC, Poirier RA (1998) Graphical approach for defining natural internal coordinates. J Comput Chem 19 504—511... 

Baker, J. (1993). Techniques for Geometry Optimization A Comparison of Cartesian and Natural Internal Coordinates. Journal of Computational Chemistry, 14,1085. 

For the representation of quadratic force fields, spectro-scopists have long been using symmetry and local internal coordinates. In quantum chemistry the use of these coordinates, called natural internal coordinates in this context, received widespread acceptance after automatic generation of these coordinates for most molecular systems had... 

If the anharmonic force field is evaluated at a nonstationary reference geometry in internal coordinates, then the internal coordinate forces can be neglected and the vibrational analysis performed as if based on a stationary reference geometry. This procedure has been widely employed. With the usual choice of internal coordinate systems (e.g., natural internal coordinates) the results obtained in this way for semirigid molecules are as accurate as possible. ... 

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