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