Dipole moments, quadrupole moments etc. and the corresponding polarizabilities
can be obtained as energy derivatives by the finite difference approximation.
This is most easily done with the `DIP`, `QUAD`, or `FIELD` commands.
An error will result if the added perturbation is not
totally symmetric (symmetry 1). Note that the orbitals must be
recomputed before performing a correlation calculation.

**Subsections**

molpro@molpro.net 2018-09-19