:term:`GUESS <GUESS (SCF)>`
"""""""""""""""""""""""""""

      The type of guess orbitals. Defaults to ``READ`` for geometry optimizations after the first step, to ``CORE`` for single atoms, and to ``SAD`` otherwise. The ``HUCKEL`` guess employs on-the-fly calculations like SAD, as described in doi:10.1021/acs.jctc.8b01089.

      * **Type**: string
      * **Possible Values**: AUTO, CORE, GWH, SAD, HUCKEL, READ
      * **Default**: AUTO

