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16.11 Advanced use: Core-excited states

Some kinds of excited or higher ionized states can be calculated using a so-called delta-SCF procedure. Here the excitation/ionization energy is obtained as difference of the SCF solutions for the ground state and the excited/ionized state. If the excited state is reasonably well described by a single determinant, this procedure is normally quite accurate.

The example

shows how to use the delta-SCF procedure to calculate the N 1s core binding energy in pyridine, by employing localized orbtials and moving them to the HOMO position using a ROTATE card (Sec. 16.5). In the core-excited state calculation, SCF is prevented from collapsing to the ground state by using the option NITORD=1 (Sec. 16.1), which asks SCF to lock onto the input solution. 2018-06-18