An input example for SIRIUS

The number of symmetries and the number of basis orbitals are read from the one-electron integral file. The number of symmetries may also be specified in the **WAVE FUNCTIONS input module as a way of obtaining a consistency check between the wave function input section and available integral files.

The following sample input specifies a CASSCF calculation on water with maximum use of defaults:

**WAVE FUNCTIONS
.MCSCF              -- specifies that this is an MCSCF calculation
*CONFIGURATION INPUT
.SPIN MULTIPLICITY  -- converge to singlet state
    1
.SYMMETRY           -- converge to state of symmetry 1 (i.e. A1)
    1
.INACTIVE ORBITALS  -- number of doubly occupied orbitals each symmetry
    1    0    0    0
.CAS SPACE          -- selects CAS and defines the active orbitals.
    4    2    2    0
.ELECTRONS          -- number of electrons distributed in the active
    8                  orbitals.
*ORBITAL INPUT
.MOSTART            -- initial orbitals are orbitals from a previous run
 NEWORB                (for example MP2 orbitals)
**(name of next input module)

Comparing to the list of necessary input information in Fig. 6.1, the following points may be noted: The number of basis functions are read from the one-electron integral file. Because no orbitals are going to be deleted, the number of molecular orbitals will be the same as the number of basis functions. No state has been specified as ground state calculation is the default. The default convergence threshold of 1.0D-5 is used.