The Charge keyword requests that a background charge distribution be included in the calculation. The charge distribution is made up of point charges [Hall84, Smith86].
By default, the charges are read from the input stream, one per line, in this format:
x y z charge
where x,y,z are the coordinates in the standard orientation (in the units specified by the Units keyword and defaulting to Angstroms), and charge is the charge.
In Gaussian 09, charges must be specified in the standard orientation (not the input orientation). Use the %KJob L301 Link 0 command to quickly determine the standard orientation for a molecule.
Angstrom
Indicates that input charge locations are specified in Angstroms.
Bohr
Indicates that input charge locations are specified in Bohrs.
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
Last update: 24 September 2015