Gaussian 03 Online Manual
This keyword requests that the molecular volume be computed, defined as the volume inside a contour of 0.001 electrons/bohr3 density. The density to be used can be specified with the Density keyword. Since a Monte-Carlo integration is done, the computed volume is only accurate to about two significant figures, but this is sufficient to estimate a radius for use with the Onsager solvent reaction field model. The recommended radius (which is 0.5Å larger than the radius corresponding to the computed volume) is printed in the output.
Since other, more accurate solvent models are available in Gaussian 03, this keyword has applicability only in preparation for frequency calculations using SCRF=Dipole.
Hartree-Fock, all DFT methods, CIS, MP2, MP3, MP4(SDQ), CID, CISD, CCD, CCSD and QCISD.