Gaussian 03 Online Manual
Last update: 2 October 2006

Charge

The Charge keyword requests that a background charge distribution be included in the calculation. The charge distribution is made up of point charges [424,425].

By default, the charges are read from the input stream, one per line, in this format:

x y z charge 0.0 A [ρ B]

where x,y,z are the coordinates in the input orientation (in the units specified by the Units keyword) and defaulting to Angstroms), charge is the charge, 0.0 is a fixed field, and the remaining items are parameters in the following equation for the additional electron repulsive term:

Angstroms
Indicates that input charge locations are specified in Angstroms.

Bohrs
Indicates that input charge locations are specified in Bohrs.

StandardOrientation

Indicates that the input charges are specified in the standard orientation rather than the input orientation. Use the %KJob=L301 Link 0 command to quickly determine the standard orientation for a molecule.

Check
Reads the background charge distribution from the checkpoint file.

Single point energies, optimizations and frequencies. Not valid with semi-empirical methods or PBC.

%KJob, Units

To perform geometry optimizations in the presence of background charges, you must use Opt=Z-Matrix NoSymm keywords and define the input geometry either in traditional Z-matrix coordinates or symbolic Cartesian coordinates. Here is an example:

# RHF/STO-3G Opt=Z-Matrix Charge NoSymm 

Water, STO-3G, point charges 

0,1 
O 
H 1 R1 
H 1 R2 2 A1 
Variables: 
R1=1.0 
R2=1.0 
A1=105. 

2.0  2.0 2.0 1.2 
2.0 -2.0 2.0 1.1