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.
Angstroms
Indicates that input charge locations are specified in Angstroms.
Bohrs
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.
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:
# B3LYP/6=31G(d) Opt=Z-Matrix Charge NoSymm
Water with point charges
0,1
O -0.75 -0.94 0.0
H 0.21 -0.94 0.0
H-1.07 -0.0 0.0
2.0 2.0 2.0 1.2
2.0 -2.0 2.0 1.1
