CCL Home Page
Up Directory CCL chelpg.man
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
Modified: Wed May 22 16:00:00 1991 GMT
Page accessed 7205 times since Sat Apr 17 21:34:25 1999 GMT