Time-dependent Hartree-Fock excited states calculation

The computation of Hartree-Fock excitation energies and oscillator strengths are currently available for restricted HF and QED-HF. A description of how to perform generic HF and QED-HF calculations are given in the Hartree-Fock calculation and QED-HF calculation tutorial. In addition to the sections that are needed for a ground state HF or QED-HF calculation, the tdhf excited state keyword must be specified in the do section:

- do
  tdhf excited state

Furthermore, you must add the solver tdhf es section and specify the number of singlet states, for instance:

- solver tdhf es
  singlet states: 2

In this same section you can specify, among other keywords, the restart, max iterations, tamm-dancoff and threshold keywords. A minimal working example is:

- do
  tdhf excited state

- memory
  available: 8

- method
  hf

- solver tdhf es
  singlet states: 2

- geometry
  basis: cc-pVDZ
  H        0.8475370000      0.0347360000      1.0345270000
  C        0.3504820000      0.0067450000      0.0608350000
  H        0.6350750000      0.8927640000     -0.5200650000
  H        0.6629360000     -0.8933800000     -0.4828330000
  O       -1.0108350000     -0.0082340000      0.3643870000
  H       -1.4851950000     -0.0326310000     -0.4568520000

If successful, you should find a summary of the excitation energies, transition dipole moments and oscillator strengths at the end of the output file:

- TDHF excitation energies:

                                    Excitation energy
                        ------------------------------------------
    State                (Hartree)             (eV)
   ---------------------------------------------------------------
      1                  0.330048904040        8.981088133311
      2                  0.406144230368       11.051747432337
   ---------------------------------------------------------------
   eV/Hartree (CODATA 2014): 27.21138602

- Summary of TDHF transition properties calculation:

   States m = 0 and n = 1:
   -------------------------
   Excitation energy [E_h]:           0.330048904040
   Excitation energy [eV]:            8.981088133311

              Transition moments [a.u.]   Transition strength [a.u.]
   ------------------------------------------------------------------
   Comp.              <m|r|n>                   |<m|r|n>|^2
   ------------------------------------------------------------------
     X             0.0003509311                0.0000001232
     Y            -0.0227066964                0.0005155941
     Z             0.0004825970                0.0000002329
   ------------------------------------------------------------------
   Oscillator strength:      0.000113525847

   States m = 0 and n = 2:
   -------------------------
   Excitation energy [E_h]:           0.406144230368
   Excitation energy [eV]:           11.051747432337

              Transition moments [a.u.]   Transition strength [a.u.]
   ------------------------------------------------------------------
   Comp.              <m|r|n>                   |<m|r|n>|^2
   ------------------------------------------------------------------
     X             0.0838600158                0.0070325022
     Y            -0.0015004221                0.0000022513
     Z            -0.1261278272                0.0159082288
   ------------------------------------------------------------------
   Oscillator strength:      0.006212106595

For QED-HF we also provide an esitmation of the photon character of the excitation.

Relevant input sections

solver tdhf es