Example: Core excitation energies: TiCl4¶
Calculation of the 2p Ti and 2p Cl core excitation energies of TiCl4
The state selective method (key SELECTEXCITATION) can be used to calculate core excitation energies. 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.
First an example with the key MODIFYEXCITATION.
$ADFBIN/adf << eor Title TiCl4 TD-DFT scalar relativistic 2p Ti core excitations Units LENGTH BOHR End Atoms Ti 0. 0. 0. Cl 2.36754 2.36754 2.36754 Cl -2.36754 -2.36754 2.36754 Cl 2.36754 -2.36754 -2.36754 Cl -2.36754 2.36754 -2.36754 End SYMMETRY T(D) EPRINT eigval 1000 1000 End XC GGA LB94 End relativistic scalar zora ModifyExcitation UseOccupied T2 2 SubEnd UseScaledZORA END Excitation ONLYSING Davidson & T2 12 SubEnd End Basis Type DZ Core None End BeckeGrid Quality good End end input eor
In this example, the 12 lowest singlet-singlet excitation energies of T2 symmetry are calculated, the dipole allowed excitations. This can also be achieved using the ALLOWED subkey in the key Excitation.
In this example only excitations from the 2t2 -orbital are included (see the key MODIFYEXCITATION), an almost pure 2p core orbital of titanium. The orbital energies of the uninteresting other occupied orbitals are artificially changed to a large negative value (-1d6 hartree).
In the second example the 2p Cl core excitation energies of TiCl4 are calculated. The difference between the first example in this one is mainly the use of the key MODIFYEXCITATION:
ModifyExcitation UseOccRange -8.0 -6.0 UseScaledZORA END
In this example only excitations from occupied orbitals are considered which have orbital energies between -8 and -6 hartree, namely the 5a1 , 1e, 1t1 , 4t2 , and 5t2 orbitals, which are almost pure 2p core orbitals of chlorine. The orbital energies of the uninteresting other occupied orbitals are again artificially changed to a large negative value (-1d6 hartree).
Another possibility is the use of the subkey OccVirtRange:
ModifyExcitation UseOccVirtRange 7.0 100.0 UseScaledZORA END
Similarly one can use the key SELECTEXCITATION.
SelectExcitation UseOccupied T2 2 SubEnd UseScaledZORA END
SelectExcitation UseOccVirtRange 7.0 100.0 UseScaledZORA END