TD Output

Name TDExcitedStatesToProject
Section Time-Dependent::TD Output
Type block

[WARNING: This is a very experimental feature] To be used with TDOutput = populations. The population of the excited states (as defined by <Phi_I|Phi(t)> where |Phi(t)> is the many-body time-dependent state at time t, and |Phi_I> is the excited state of interest) can be approximated – it is not clear how well – by substituting for those real many-body states the time-dependent Kohn-Sham determinant and some modification of the Kohn-Sham ground-state determinant (e.g., a simple HOMO-LUMO substitution, or the Casida ansatz for excited states in linear-response theory. If you set TDOutput to contain populations, you may ask for these approximated populations for a number of excited states, which will be described in the files specified in this block: each line should be the name of a file that contains one excited state.

This file structure is the one written by the casida run mode, in the files in the directory *_excitations. The file describes the "promotions" from occupied to unoccupied levels that change the initial Slater determinant structure specified in ground_state. These promotions are a set of electron-hole pairs. Each line in the file, after an optional header, has four columns:

i a $\sigma$ weight

where i should be an occupied state, a an unoccupied one, and $\sigma$ the spin of the corresponding orbital. This pair is then associated with a creation-annihilation pair $a^{\dagger}{a,\sigma} a{i,\sigma}$, so that the excited state will be a linear combination in the form:

$\left|{\rm ExcitedState}\right> = \sum weight(i,a,\sigma) a^{\dagger}{a,\sigma} a{i,\sigma} \left|{\rm GroundState}\right>$

where weight is the number in the fourth column. These weights should be normalized to one; otherwise the routine will normalize them, and write a warning.

Name TDFloquetDimension
Section Time-Dependent::TD Output
Type integer
Default -1

Order of Floquet Hamiltonian. If negative number is given, downfolding is performed.

Name TDFloquetFrequency
Section Time-Dependent::TD Output
Type float
Default 0

Frequency for the Floquet analysis, this should be the carrier frequency or integer multiples of it. Other options will work, but likely be nonsense.

Name TDFloquetSample
Section Time-Dependent::TD Output
Type integer
Default 20

Number of points on which one Floquet cycle is sampled in the time-integral of the Floquet analysis.

Name TDMultipoleLmax
Section Time-Dependent::TD Output
Type integer
Default 1

Maximum electric multipole of the density output to the file td.general/multipoles during a time-dependent simulation. Must be non-negative.

Name TDOutput
Section Time-Dependent::TD Output
Type block
Default multipoles + energy (+ others depending on other options)

Defines what should be output during the time-dependent simulation. Many of the options can increase the computational cost of the simulation, so only use the ones that you need. In most cases the default value is enough, as it is adapted to the details of the TD run. If the ions are allowed to be moved, additionally the geometry and the temperature are output. If a laser is included it will output by default.

Note: the output files generated by this option are updated every RestartWriteInterval steps.

Example:

%TDOutput
  multipoles
  energy
%

Options:

• multipoles:
  Outputs the (electric) multipole moments of the density to the file td.general/multipoles. This is required to, e.g., calculate optical absorption spectra of finite systems. The maximum value of $l$ can be set with the variable TDMultipoleLmax.
  
• angular:
  Outputs the orbital angular momentum of the system to td.general/angular, which can be used to calculate circular dichroism.
  
• spin:
  (Experimental) Outputs the expectation value of the spin, which can be used to calculate magnetic circular dichroism.
  
• populations:
  (Experimental) Outputs the projection of the time-dependent Kohn-Sham Slater determinant onto the ground state (or approximations to the excited states) to the file td.general/populations. Note that the calculation of populations is expensive in memory and computer time, so it should only be used if it is really needed. See TDExcitedStatesToProject.
  
• geometry:
  If set (and if the atoms are allowed to move), outputs the coordinates, velocities, and forces of the atoms to the the file td.general/coordinates. On by default if MoveIons = yes.
  
• dipole_acceleration:
  When set, outputs the acceleration of the electronic dipole, calculated from the Ehrenfest theorem, in the file td.general/acceleration. This file can then be processed by the utility oct-harmonic-spectrum in order to obtain the harmonic spectrum.
  
• laser:
  If set, outputs the laser field to the file td.general/laser. On by default if TDExternalFields is set.
  
• energy:
  If set, octopus outputs the different components of the energy to the file td.general/energy. Will be zero except for every TDEnergyUpdateIter iterations.
  
• td_occup:
  (Experimental) If set, outputs the projections of the time-dependent Kohn-Sham wavefunctions onto the static (zero-time) wavefunctions to the file td.general/projections.XXX. Only use this option if you really need it, as it might be computationally expensive. See TDProjStateStart. The output interval of this quantity is controled by the variable TDOutputComputeInterval In case of states parallelization, all the ground-state states are stored by each task.
  
• local_mag_moments:
  If set, outputs the local magnetic moments, integrated in sphere centered around each atom. The radius of the sphere can be set with LocalMagneticMomentsSphereRadius.
  
• gauge_field:
  If set, outputs the vector gauge field corresponding to a spatially uniform (but time-dependent) external electrical potential. This is only useful in a time-dependent periodic run. On by default if GaugeVectorField is set.
  
• temperature:
  If set, the ionic temperature at each step is printed. On by default if MoveIons = yes.
  
• ftchd:
  Write Fourier transform of the electron density to the file ftchd.X, where X depends on the kick (e.g. with sin-shaped perturbation X=sin). This is needed for calculating the dynamic structure factor. In the case that the kick mode is qbessel, the written quantity is integral over density, multiplied by spherical Bessel function times real spherical harmonic. On by default if TDMomentumTransfer is set.
  
• dipole_velocity:
  When set, outputs the dipole velocity, calculated from the Ehrenfest theorem, in the file td.general/velocity. This file can then be processed by the utility oct-harmonic-spectrum in order to obtain the harmonic spectrum.
  
• eigenvalues:
  Write the KS eigenvalues.
  
• ionization_channels:
  Write the multiple-ionization channels using the KS orbital densities as proposed in C. Ullrich, Journal of Molecular Structure: THEOCHEM 501, 315 (2000).
  
• total_current:
  Output the total current (average of the current density over the cell).
  
• partial_charges:
  Bader and Hirshfeld partial charges. The output file is called 'td.general/partial_charges'.
  
• td_kpoint_occup:
  Project propagated Kohn-Sham states to the states at t=0 given in the directory restart_proj (see %RestartOptions). This is an alternative to the option td_occup, with a formating more suitable for k-points and works only in k- and/or state parallelization
  
• td_floquet:
  Compute non-interacting Floquet bandstructure according to further options: TDFloquetFrequency, TDFloquetSample, TDFloquetDimension. This is done only once per td-run at t=0. works only in k- and/or state parallelization
  
• n_excited_el:
  Output the number of excited electrons, based on the projections of the time evolved wave-functions on the ground-state wave-functions. The output interval of this quantity is controled by the variable TDOutputComputeInterval
  
• coordinates_sep:
  Writes geometries in a separate file.
  
• velocities_sep:
  Writes velocities in a separate file.
  
• forces_sep:
  Writes forces in a separate file.
  
• total_heat_current:
  Output the total heat current (average of the heat current density over the cell).
  
• total_magnetization:
  Writes the total magnetization, where the total magnetization is calculated at the momentum defined by TDMomentumTransfer. This is used to extract the magnon frequency in case of a magnon kick.
  
• photons_q:
  Writes photons_q in a separate file.
  
• maxwell_field:
  Writes total electric field (if coupling is in length_geuge) or vector potential (if coupling is in velocity_gauge) coming from the interaction with Maxwell systems (only if Maxwell-TDDFT coupling is in dipole).
  
• norm_ks_orbitals:
  Writes the norm of each Kohn-Sham orbital. The data is ordered per row as: Iteration time (state 1 kpoint 1) (state2 kpoint1) ... (state-Nstates kpoint1) (state1 kpoint2) ... (state-Nstates kpoint-nkpt) noting that the kpoint index will also include the spin index for spin-polarised calculations.
  

Name TDOutputComputeInterval
Section Time-Dependent::TD Output
Type integer
Default 50

The TD output requested are computed when the iteration number is a multiple of the TDOutputComputeInterval variable. Must be >= 0. If it is 0, then no output is written. Implemented only for projections and number of excited electrons for the moment.

Name TDOutputDFTU
Section Time-Dependent::TD Output
Type flag
Default none

Defines what should be output during the time-dependent simulation, related to DFT+U.

Note: the output files generated by this option are updated every RestartWriteInterval steps.

Options:

• effective_u:
  Writes the effective U for each orbital set as a function of time.
  

Name TDOutputResolveStates
Section Time-Dependent::TD Output
Type logical
Default No

Defines whether the output should be resolved by states.

So far only TDOutput = multipoles is supported.

Name TDProjStateStart
Section Time-Dependent::TD Output
Type integer
Default 1

To be used with TDOutput = td_occup. Not available if TDOutput = populations. Only output projections to states above TDProjStateStart. Usually one is only interested in particle-hole projections around the HOMO, so there is no need to calculate (and store) the projections of all TD states onto all static states. This sets a lower limit. The upper limit is set by the number of states in the propagation and the number of unoccupied states available.