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50.2 Recommendations

It is recommended to split up the calculations in three parts: (1) Do a very accurate geometry optimization and bring the optimized geometry into standard orientation (using the MASS keyword. Start a second calculation based on the optimized geometry and do (2) a harmonic frequency calculation which should be stored in the restart-file (.wfu). Make a backup of the restart-file. (3) Start a SURF, VSCF and VCI calculation from the restart-file (.wfu) and dump the potential energy surfaces to an external file (using the DUMP keyword). Later on you can restart your VSCF and VCI calculations from this external file without recomputing the surface.