MOLPRO

48 POLYNOMIAL REPRESENTATIONS (POLY) 362
48 POLYNOMIAL REPRESENTATIONS (POLY)
POLY,options
The POLY program allows for the transformation of the potential energy surface and dipole
surfaces from a grid representation to a polynomial representation. Once a polynomial representation
has been chosen, the corresponding VSCF, VCI or VMP2 programs need to be selected
(see below). The POLY program is fully parallelized in terms of the MPPX scheme.
48.1 Options
The following options are available:
NDIM=value
NGRID=value
ORDPOL=value
ORDPROD=value
DIPOLE=value
PMP=value
SHOW=value
The keyword NDIM=n terminates the transformation after the nD terms
within the n-mode expansion of the surfaces. The default is set to 3.
The transformation of the 4D terms can be very time consuming.
Once the value of the NGRID=n keyword for controlling the number
of grid points has been changed in the SURF program, this information
needs to be passed to the POLY program.
This keyword controls the order of the polynomial to be determined
in the fitting procedure. The default is set to 6.
In multidimensional fitting the maximum order of the polynomial is
not given by ORDPOL times the dimension, but rather by ORDPROD.
The default is set to 12. This reduces the computational cost for fitting
tremendously. However, for accurate calculations ORDPROD=8 and
ORDPOL=18 are recommended.
In case that dipole surfaces have been computed, they need to be transformed
to a polynomial representation as well. This can be accomplished
by DIPOLE=1.
The Watson correction term, i.e. PMP=1, usually is absorbed in the
potential. Once the polynomials to be generated should include this
correction, this needs to be specified. Any other values, i.e. 2 or 3,
will be ignored.
The coefficients of the polynomial representation can be printed. In
order to identify quartic potentials, it is recommended to use SHOW=1.
Higher values will lead to a very long output file.