Atoms In Molecules (AIM)

Information on the Atoms In Molecules (AIM) scheme can be found on the following sites:
 

• the AIM2000 web page
• the web page of Paul Popellier

The AIM version in Gaussian can be used with the aim keyword. The following input file will perform a minimal AIM analysis in order to obtain AIM atomic charges:
 

#P HF/STO-3G scf=(direct,tight) aim=charges 

test29 HF/STO-3G formaldehyde AIM  

0 1
C1
O2 1 r2
H3 1 r3 2 a3
H4 1 r3 2 a3 3 180.

r2=1.21672
r3=1.10138
a3=122.73682

A full AIM analysis can be performed with aim=all.

A detailed overview of the performance of the AIM method in describing the charge distribution in water can be found in: F. Martin, H. Zipse, J. Comp. Chem. 2005, 26, 97 - 105. A copy of the pdf file is available here.