Keywords for redundant internal coordinates in

`ired`

option. Important options are:
- [
`iprint`*n*]

print parameter for debug output: The larger*n*is, the more output is printed(default: 0)*n*≥ 0,*n*≤ 5 - [
`metric`*n*]

method for generating and processing of redundant internal coordinates

(default: 3)*n*≥ - 3,*n*≤ 3,*n*≠ 0

Values for the

`metric`option:`n = 1`- ``Delocalized Coordinates''

Thematrix is diagonalized for the complete set of redundant internal coordinates, matrix**BmB**^{t}is a unit matrix.**m** `n = -3`- Delocalized Coordinates obtained
with a modified matrix
, the values of**m**can be defined by user input (see below).**m** `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
option, but for the remaining cage delocalized coordinates with modified matrix*n*= 1are defined as for**m**.*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**. Thematrix is diagonalized for each block separately after the columns of**BB**^{t}were orthogonalized against the columns of**B**of the the preceding blocks.**B** `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 matrixin**m**.**BmB**^{t}