MOLPRO

42 GEOMETRY OPTIMIZATION (OPTG) 311
COORD,[opt space],[opt coord],[NOROT]
These options choose the optimization space and the coordinate system in which the optimization
takes place.
opt space defines the parameters to be optimized. By default, if the geometry input is given
in Z-matrix format, all variables on which the Z-matrix depends are optimized. Subsets of
the variables on which the Z-matrix depends can be chosen using the ACTIVE or INACTIVE
subdirectives. If the Z-matrix depends on no variables or xyz input is used, all 3N cartesian
coordinates are optimized.
opt space can be one of the following:
ZMAT
3N
Optimize all variables on which the Z-matrix depends (default if the
geometry is given as Z-matrix).
Optimize all 3N cartesian coordinates (default if the Z-matrix depends
on no variables, or if xyz-input is used). Z-Matrix input coordinates
will be destroyed if 3N is used..
opt coord determines the coordinates in which the optimization takes place. By default, local
normal coordinates are used. Optionally cartesian coordinates or natural internal coordinates
can be used.
opt coord can be one of the following:
NORMAL
NONORM
BMAT[=filename]
Optimization in local normal coordinates. This is default if the Model
Hessian is used to approximate the Hessian.
Don’t use local normal coordinates.
Use Pulay’s natural internal coordinates, see G. Fogarasi, X. Zhou,
P. W. Taylor and P. Pulay J. Am. Chem. Soc. 114, 8191 (1992); P.
Pulay, G. Fogarasi, F. Pang, J. E. Boggs J. Am. Chem. Soc. 101, 2550
(1979)). Optionally, the created coordinates as well as additional informations
about this optimization are written to the specified file.
These coordinates resemble in part the valence coordinates used by
vibrational spectroscopist, and have the advantage of decreasing coupling
between different modes. This often increases the speed of convergence.
The use of this option is highly recommended, especially
in minimization of large organic molecules with rings. Nevertheless
you should keep in mind that these coordinates are constructed automatically,
and there exist exotic bond structures which might not
be treated properly (e.g. weakly bonded species as in transition state
optimizations). In such a case, if the BMAT optimization converges
slowly or leads to symmetry-breaking errors, you should try another
optimization method and/or cartesian or Z-Matrix coordinates.
If the option [NOROT] is given, the cartesian coordinates are not transformed to minimize rotations.
42.2.3 Displacement coordinates (DISPLACE)
DISPLACE,displacement type
see section 41.2.1 for details.