Prerequisites

Both dscf and ridft require the control file and starting orbitals obtained from the extended Hückel guess using define.

Energy calculations using dscf can be performed in a direct or semi-direct mode. In the direct mode all four-center ERI's are recalculated at each SCF iteration. The semi-direct mode uses a selective storage of the most time consuming and frequently used integrals. The amount of integrals stored is controlled by the keywords $thize and $thime, related to integral size and computational cost. The semi-direct mode requires a separate dscf statistics run to estimate the disk space needed for integral storage. The statistics run requires the keyword $statistics dscf to be present in the control file. It can be set either manually or using the tool Stati.

For ridft and rdgrad following additional prerequisites are required:

1. An auxiliary basis defined in the data group $jbas. This group is created automatically when using ri menu of define.
2. The maximum core memory the program is allowed to allocate should be defined in the data group $ricore; the recommended value is 75-85% of the available (physical) core memory.
3. Calculations using MARI-J method require the keyword $marij.
4. For RI-HF-calculations auxiliary bases defined in the data group $jkbas are needed. This group is created by the rijk menu in define.