The START directive can be used to specify the initial orbitals used in the
SCF iteration. It is either possible to generate an initial orbital guess, or
to start with previously optimized orbitals. Alternatively, one can also use
a previous density matrix to construct the first fock operator.
If the START card is absent, the program tries to find suitable starting orbitals as follows:
Since these defaults are usually appropriate, the START card is not required
in most cases.
- Try to read orbitals from record specified on the ORBITAL
or SAVE card or the corresponding default (see ORBITAL). All files are
- Try to find orbitals from a previous SCF or MCSCF calculation. All files are
- If no orbitals are found, the starting orbitals are generated using
approximate atomic densities or eigenvectors of (see below).