C H E L P G vsn 12/18/90 - no vectorization (yet)
C. Breneman
- A MODIFICATION OF CHELP (DEVELOPED BY L. E. CHIRLIAN)
"Determining Atom-Centered Monopoles from Molecular Electrostatic
Potentials. The Need for High Sampling Density in Formamide
Conformational Analysis" J. Comput. Chem., 11, 361-373 (1990).
Curt M. Breneman and Kenneth B. Wiberg
THE "G" STANDS FOR GRID. A GRID IS SEARCHED, AND EACH POINT IN THE GRID
(SIZE = X,Y,Z MOLECULE DIMENSIONS + RMAX, DELR = DISTANCE BETWEEN POINTS
IN THE GRID). Points within the V.D.W. radii of the molecule are removed.
Thus the number of points and the position of the points are chossen
automatically. THis differs from CHELP which uses a shell method of placing
sampling points
The monopole charge condensation of the electron density described
by the point charge distribution is obtained by a Lagrange least-squares method..
Input:
CHELPG INPUT FILE example for water:
wsto3g.CHK <- checkpoint file name
CHELPG90 calculation, short radii <- titles, end with blank line
Water, STO-3G by Gaussian 90
1 0 0 0 0 <- debug codes, use as is or all 0
6 <- # of D functions (5 or 6)
1.7, 1.45, 1.45 <- free format v.d.w exclusion radii
0 <- total # of points - leave zero
1.0 <- v.d.w scale factor
2.8, 0.3 <- RMAX, DELR see paper
Recommended van der Waal (exclusion) radii have not yet been
standardized. The paper referenced above describes data using two flavors,
short and long:
C 1.5, 2.0
N 1.7, 2.0
O 1.7, 2.0
H 1.45, 1.5
The larger exlusion radii result in less positive carbon atoms and
less negative oxygen atoms.
Test files:
run g90 calc:
%CHK=wsto3g.CHK
# RHF/sto-3g
water sto-3g structure constrained
experimental geometry (example #1 g86)
0 1
O
H 1 0.956
H 1 0.956 2 104.5
output: (run on g88)
standard coordinates (in Bohr) from checkpoint file
basis and shell information
total points considered = 8280
number of points selected = 3953
net charges
O -0.6182
H 0.3091
H 0.3092
RMS = 0.0082 kcal/mol
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