START,[RECORD=]record.file,[specifications]
reads previously optimized orbitals from record record on file file. Optionally, a specific orbital set can be specified as described in section 2.16.
The specified dump record may correspond to a different geometry, basis set, and/or symmetry than used in the present calculation. Using starting orbitals from a different basis set can be useful if no previous orbitals are available and the ATDENS option cannot be used (see above).
The following example shows how to change the symmetry between scf calculations. Of course, this example is quite useless, but sometimes it might be easier first to obtain a solution in higher symmetry and then convert this to lower symmetry for further calculations.
Input: h2o_c2v_cs_start.com Output: h2o_c2v_cs_start.out
Note, however, that this only works well if the orientation of the molecule does not change. Sometimes it might be helpful to use the noorient option.
Note also that a single dump record cannot hold orbitals for different basis dimensions. Using save=2100.2 in the second calculation would therefore produce an error.
If orbitals from a corresponding SCF calculation at a neighbouring geometry are available, these should be used as starting guess.
P.J. Knowles and H.-J. Werner