TDDFT calculations with DIRAC
From Diracwiki
Here I would like to give a typical input for a TDDFT calculation of excitation energies with DIRAC and discuss the important keywords (colored).
This is a TDDFT calculation of the Zn atom with the PBE functional.
To obtain good TDDFT excitation energies it is essential to include the spin density contribution (spin magnetization contribution). This is done with the .SDFT keyword. Without spin density, triplet excitation energies correspond to KS orbital energy differences.
We suppress orbital rotations between positive and negative energy orbitals with .SKIPEP.
Also include the .TRIPLET keyword. This keyword is without effect (but also without harm) when spin-orbit coupling is turned on. However, without spin-orbit coupling (nonrelativistic or spin-free calculations) this keyword allows the spin density contribution in spin-forbidden transitions. Without spin-orbit coupling and without .TRIPLET, triplet energies again correspond to KS orbital energy differences. This keyword does not mean that only triplet states are solved for.
**DIRAC .WAVE FUNCTION .PROPERTIES .ANALYZE **HAMILTONIAN .LVCORR .DFT PBE *DFT .SDFT **INTEGRALS *READIN .UNCONTRACT **WAVE FUNCTION .DHF *DHFCAL .EVCCNV 1.0D-9 1.0D-6 .CLOSED 18 12 !zinc atom **PROPERTIES *EXCITATION ENERGIES .TRIPLET .SKIPEP .ANALYZE .EXCITATION ENERGIES 3 4 .EXCITATION ENERGIES 5 4 .EXCITATION ENERGIES 8 4 .OPERATOR XDIPLEN .OPERATOR YDIPLEN .OPERATOR ZDIPLEN **ANALYZE .MULPOP *MULPOP .VECPOP 1..oo 1..oo !remove this line if there is only one Fermion irreducible corepresentation *END OF
With
.EXCITATION ENERGIES
3 4
.EXCITATION ENERGIES
5 4
.EXCITATION ENERGIES
8 4
we ask for the four lowest excitation energies in the irreps 3, 5, and 8.
In this example (Zn, D2h) these are the ungerade irreps B2u, B1u, and Au.
Finally, it is a good idea to always include
.OPERATOR
XDIPLEN
.OPERATOR
YDIPLEN
.OPERATOR
ZDIPLEN
to get transition dipole moments and oscillator strengths (if symmetry allowed).
