Core excitation energies: TiCl₄

Sample directory: adf/TiCl4_CoreExci/

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

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