ABSTRACT
Very often the isodensity surface corresponding to 0.002 au is used since that surface corresponds roughly to the molecular volumes measured for small gas phase molecules. These volumes are also well represented by the surface described by interlocking spheres of atomic spheres with a particular set of radii, known as van der Waals spheres. Most graphics programs can display molecules this way, and it is generally an accurate and efficient way of approximating the isodensity surface.
