32.1 Structure of the input

All CASVB sub-commands may be abbreviated by four letters. The general input structure can be summarized as follows:

a)

For generating representations of CASSCF wavefunctions, the program is invoked by the command CASVB. For variational optimization of wavefunctions it is normally invoked inside MULTI by the sub-command VB (see 16.10).

b)

Definition of the CASSCF wavefunction (not generally required).

c)

Definition of the valence bond wavefunction.

d)

Recovery and/or storage of orbitals and vectors.

e)

Manual input of starting guess (optional).

g)

Optimization control.

f)

Definition of molecular symmetry and possible constraints on the VB wavefunction.

h)

Wavefunction analysis.

i)

Further general options.

Items a) and b) should precede everything else in the input; apart from this, commands may come in any order.