# Example: Excitation energies perturbative spin-orbit coupling: AgI¶

Download AgI_asoexcit.run

Calculation of the excitation energies of AgI including spin-orbit coupling in a perturbative way.

\$ADFBIN/adf << eor
Title [AgI]
Atoms
Ag .0000  .0000  2.5446
I .0000  .0000  0.0000
End
relativistic scalar zora
symmetry C(7v)
Excitations
lowest 60
End
SOPERT
NumericalQuality Good
Basis
Type TZ2P
Core None
End
eor


ADF can not handle ATOM and linear symmetries in excitation calculations. Therefore a subsymmetry is used, in this case symmetry C(7v).

For such a small molecule, a relatively small TZ2P basis set is used, which is not sufficient for excitations to Rydberg-like orbitals, one needs more diffuse functions. For larger molecules a TZ2P basis set is in most cases sufficient. In that case one might even consider smaller basis sets.

The key SOPERT is included in scalar relativistic ZORA calculations of excitation energies. First scalar relativistic TDDFT calculations are performed to determine the lowest 60 singlet-singlet and singlet-triplet excited states and the spin-orbit coupling operator is applied to these single-group excited states to obtain the excitation energies with spin-orbit coupling effects included.