Example: TDHF excitation energies: N2¶
Calculation of the excitation energies of N2 using time-dependent Hartree-Fock (TDHF). It also shows the possibility to use the Tamm-Dancoff approximation (TDA). This examples consists of 4 calculations:
- non-relativistic TDHF
- spin-orbit coupled TDHF
- non-relativistic TDHF, TDA
- spin-orbit coupled TDHF, TDA
The results will be inaccurate due to small basis set. The key ADDDIFFUSEFIT is required for a more accurate fit of the density.
$ADFBIN/adf << eor
Atoms
N 0 0 0
N 0 0 1.0977
End
XC
hartreefock
end
dependency bas=1e-4
adddiffusefit
Basis
Type DZ
Core None
End
BeckeGrid
Quality Good
End
excitations
lowest 5
end
End Input
eor
In case of spin-orbit coupling one needs to include the key RELATIVISTIC with argument ZORA SPINORBIT. In practice one needs to calculate more excitations if one includes spin-orbit coupling, since the singlet-singlet and singlet-triplet excitations are not calculated separately, but will be treated simultaneously, since they may mix.
excitations
lowest 20
end
relativistic spinorbit zora
The Tamm-Dancoff approximation (TDA) will be used if one includes the key TDA. The calculation is then effectively a CIS calculation.
TDA