Example: (Core) Excitation energies including spin-orbit coupling: Ne¶
Calculation of the (core) excitation energies of Ne including spin-orbit coupling.
The state selective method (key SELECTEXCITATION) can be used to reduce the computational costs of, for example, core excitation energies. In this scheme a guess vector for the orbital transition has to be provided. It should be used in combination with the Davidson method to calculate excitation energies. An overlap criterion is used to follow the wanted eigenvector. This key can also be used in case of spin-orbit coupling. The use of the key SELECTEXCITATION is similar as the use of the key MODIFYEXCITATION. However, the key SELECTEXCITATION can not be used in combination with the key MODIFYEXCITATION. In the state selective method (key SELECTEXCITATION) the one-electron excited state configuration space remains complete, whereas it is reduced in case the scheme with the MODIFYEXCITATION key.
$ADFBIN/adf << eor Title Ne Atoms Ne .0000 .0000 0.0000 End Basis Type QZ4P End relativistic scalar zora symmetry d(8h) NumericalQuality Good xc model SAOP end Excitations lowest 10 End *ModifyExcitation UseOccupied A1.g 1 SubEnd UseScaledZORA END * End input eor mv TAPE21 Frag.t21 rm logfile TAPE21 $ADFBIN/adf << eor Title Ne spin-orbit Atoms Ne .0000 .0000 0.0000 f=Frag End relativistic spinorbit zora symmetry d(8h) xc model SAOP end NumericalQuality Good Excitations lowest 12 End *SelectExcitation UseOccupied E1/2.g 1 SubEnd UseScaledZORA END * Fragments Frag Frag.t21 End STCONTRIB End input eor
The difference between the core excitation calculation and the standard excitation is the extra subkey MODIFYEXCITATION or SELECTEXCITATION in the core excitation calculation (in italic).
ADF can not handle ATOM and linear symmetries in excitation calculations. Therefore a subsymmetry is used, in this case symmetry d(8h).
A relatively large QZ4P basis set is used, which is still insufficient for excitations to Rydberg-like orbitals, one needs more diffuse functions.
The key STCONTRIB is used, which will give a composition of the spin-orbit coupled excitation in terms of singlet-singlet and singlet-triplet scalar relativistic excitations. In order to use the key STCONTRIB the scalar relativistic fragment should be the complete molecule.
In this case the key MODIFYEXCITATION or SELECTEXCITATION takes care that only excitations from the occupied 1s-orbital (spinor) are included. In symmetry d(8H) the 1s-orbital (spinor) is of A1.g (E1/2.g) symmetry.