Gaussian keeps volumetric properties in the Gaussian cube file format. Cube files from a gaussian calculation could be generated using the cubegen and cubman programs from the Gaussian distribution.
Prerequisite is that you have saved a checkpoint file from your calculation by adding a %Chk=filename.chk statement to the header of your gaussian input file. The (binary) checkpoint file needs to be converted into a formatted file using the formchk utility (formchk filename.chk will produce the file filename.fchk). After these preparations several kinds of cube files could be generated using cubegen.
Send all questions, suggestions and comments to Vlad (email@example.com)
Dr. Vladislav Vasilyev
The Australian National University,
Canberra, ACT, 0200, Australia