TD-DFT is possible to calculate excited state that has different spin with the reference state. Here, we give some examples for such calculation.


= Some important issues =

== Integral direct TDDFT ==
Since TDDFT is a capable to study medium to large molecules, so called integral-direct method is preferred in TD-DFT calculation. To apply integral-direct TDDFT, integral-direct SCF should be evoked that fully avoids to store electronic repulsive integrals in disk. Thus, molecules with several tens or even hundred of atoms are possible via TDDFT calcualiton. 

= Examples of spin-flip TDDFT =
Here, we give some examples to perform spin-flip TDDFT calculation.

== Spin-flip TDDFT to calculate triplet state of H2O molecule ==
We start from ground state of H2O. It is a close shell ^1A1 state.