**chargefit.f and points.f**

**Chargefit** fits charges to the electrostatic potential calculated
in points around the molecule or to the electrostatic moments. The moments
or potentials are read from a gaussian (or turbomole) outputfile.

In the Gaussian calculation the IOp(6/32=3) option is used to write
the potential to the output file.

The moments can be used as constraints as well as restraints. The potential
points can be weighted with Boltzmann weights.

**Points** reads coordinates from an gaussian output file or from
an other file containing atom names and coordinates (for a description
of the format of this file se the program) and calculates randomly spaced
points around the molecule for ESP calculation.. The maximum distance from
any atom can be set to any value (we recomend 8 Angstrom). No minimal distance
is needed since points with Boltsmann weights lower than 10^-6 are discarded.
The result is written as a Gaussian inputfile for a ESP calculation.

The two programs points and chargefit are used for calculations of charges
according to the chelp-bow or the chelmo method described in our paper
(J. Comp. Chem. 19, 377-395, (1998)).

For the CHELMO method you use only chargefit. You need an outputfile
from Gaussian with electrostatic moments calculated to be used as an input
file for chargefit. Constrain to total charge and moments according
to our paper.

For the CHELP-BOW you need first to run points to generate points to
be used for electrostatic potential calculations. Points can read coordinates
from an gaussian output file. We found this to be practical since we normally
have done an energy calculation or an geometry optimisation before this
calculation. Alternatively the coordinates can be read from a file with
just atom names and coordinates (use for example a gaussian input file
with the first lines removed). Points generates a Gaussian input file.

After running Gaussian, chargefit is to be used. This time you
constrain to total charge and dipole moment according to our paper and
restrain to Boltzmann weighted potential.

On our SGI machins we have compiled chargefit with f77 and it also needs
the lapack routine dgesvd. This can be fetched at: http://www.netlib.org/lapack/

Points have been compiled with f90.

The current versions of the programs work with Gaussian94.

**Alternative versions of the programs**
**chargefit_b - **handles lonepair centras (Be) slightly better
(constrain them to have the same value if they are bound to the same atom
and does not confuse them with heavy atoms), write some lists that Bruce
are interested in and has an option of removing all points with weights
less than 0.99 in the fit.
**chargefit_w - **special version that reads in water coordiantes
and calculates the interaction energy
**chargefitconf - **alternative code to read in several conformations,
from several gaussian files with electrostatic potentials. The comparisons
to the potantial, moments etc. in the output file is not correct. If you
want these comparisons run chargefit.f with the gaussian file you want
to compare to and fix all the charges to the values obtained from chargefitconf.f.

**chargecomp.f**

Reads in several sets of alternative charges and compare them to potantials
and moments in a gaussian file.

Originally made by Ulf Ryde.

**chcoord.f**

Reads in a turbomole coord file and change the number of the internal
coordinates according to a "change file" with the old and new numbers.

**tilt.f and pilt.f**

Calculates the tilt of the A-ring in a porphyrin, as the angle between
the plane defined by the nitrogen and the two outer carbons of one pyrrole
ring and the plane defined by the remaining three nitrogens. tilt.f uses
a turbomole coord-file, and needs the atoms as an input. pilt.f uses a
pdb file as the input and find the atoms from the atom names. pilt.f is
made by Ulf Ryde.

**tiltanalys.f**

Improvement of pilt.f to calculate the tilt of all four rings. Not
completed.