The interface to the gOpenMol program offers an alternative visualization possibility, and is described in section 33.8.
The example below generates all the information required to plot the molecular orbitals of water, and to visualize the normal modes of vibration:
The example below does a difference density by presenting its natural orbitals to MOLDEN. Note that it although MOLDEN has internal features for difference density plots, the approach show here is more general in that it bypasses the restriction to STO-3G, 3-21G, 4-31G and 6-31G basis sets.