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## Keywords for redundant internal coordinates in $redund_inp With the parameters in$redund_inp the generation of redundant internal coordinates can be modified. All entries have to be made in the control file before invoking the ired option. Important options are:
• [iprint n]
print parameter for debug output: The larger n is, the more output is printed n≥ 0, n≤ 5 (default: 0)
• [metric n]
method for generating and processing of redundant internal coordinates
n≥  - 3, n≤ 3, n ≠ 0 (default: 3)

Values for the metric option:

n = 1
Delocalized Coordinates''
The BmBt matrix is diagonalized for the complete set of redundant internal coordinates, matrix m is a unit matrix.
n = -3
Delocalized Coordinates obtained with a modified matrix m, the values of m can be defined by user input (see below).
n = -1
Hybrid Coordinates''
Natural internal coordinates are defined as in the old iaut option. If a cage remains, delocalized coordinates (as for n=1) are defined for the cage.
n = -2
Very simular to the n = 1 option, but for the remaining cage delocalized coordinates with modified matrix m are defined as for n = - 3.
n = 2
Decoupled coordinates''
The redundant coordinates are divided into a sequence of blocks. These are expected to have decreasing average force constants, i.e. stretches, angle coordinates, torsions and weak'' coordinates. The BBt matrix is diagonalized for each block separately after the columns of B were orthogonalized against the columns of B of the the preceding blocks.
n = 3
Generalized natural coordinates''
Natural internal coordinates are defined first, for the remaining cage decoupled coordinates are defined.
• [type r]
a positive real number, which is an approximate force constant'', can be read in for each type of coordinate (see below). The force constants are used for the definition of the matrix m in BmBt.

Subsections

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