Skip to content

rttddft input variables

This document lists and provides the description of the name (keywords) of the rttddft input variables to be used in the input file for the abinit executable.

dtele

Mnemonics: Delta Time for ELEctrons
Mentioned in topic(s): topic_RTTDDFT
Variable type: real
Dimensions: scalar
Default value: 0.1
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [8/1314] in all abinit tests, [2/178] in abinit tutorials

Defines the electron time step in atomic units of time, used to integrate the time-dependent Kohn-Sham equations in real-time TDDFT topic_RTTDDFT if [optdriver]] is 9. (One atomic time unit is 2.418884e-17 seconds). One should also set the number of time steps to be performed using the parameter ntime.

A good value for dtele is usually less than or equal to 0.1. The user should try several values in order to find the one allowing for a stable and efficient integration.

prtcurrent

Mnemonics: PRinT macroscopic CURRENT density
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: 10

Test list (click to open). Rarely used, [3/1314] in all abinit tests, [1/178] in abinit tutorials

If set to 1, prints the time-dependent macroscopic current density computed in real-time TDDFT calculations (optdriver 9).

td_ef_ezero

Mnemonics: Time-Dependent Electric Field EZERO
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0.1
Only relevant if: optdriver is 9 and td_ef_type is not 0
Added in version: 10

Test list (click to open). Rarely used, [0/1314] in all abinit tests, [0/178] in abinit tutorials

This variable is the intensity (in atomic units) of the external electric field applied (see td_ef_type).

td_ef_induced_vecpot

Mnemonics: Time-Dependent Electric Field INDUCED VECtor POTential
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver is 9 and td_ef_type is not 0
Added in version: 10

Test list (click to open). Rarely used, [1/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls wether we include the induced vector potential in the Hamiltonian so that the total vector potential applied is the sum of the vector potential associated with the external electric field and the vector potential induced by the current density.

td_ef_pol

Mnemonics: Time-Dependent Electric Field POLarization
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: (3)
Default value: [1.0, 0.0, 0.0]
Only relevant if: optdriver is 9 and td_ef_type is not 0
Added in version: 10

Test list (click to open). Rarely used, [0/1314] in all abinit tests, [0/178] in abinit tutorials

This variable is the polarization vector (direction) of the external electric field applied (see td_ef_type).

td_ef_type

Mnemonics: Time-Dependent Electric Field TYPE
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [3/1314] in all abinit tests, [1/178] in abinit tutorials

This variable controls the type of external electric field to apply in RT-TDDFT. As of now, only impulse electric field are implemented, td_ef_type is 1. Moreover, the response to such impulse electric field can only be performed within the PAW approach (see topic_PAW). The intensity of the Dirac pulse as well as the time at which it is applied are controlled by the parameters td_ef_ezero and td_ef_tzero. If td_ef_type is 0, no electric field is applied.

td_ef_tzero

Mnemonics: Time-Dependent Electric Field TZERO
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0.0
Only relevant if: optdriver is 9 and td_ef_type is not 0
Added in version: 10

Test list (click to open). Rarely used, [3/1314] in all abinit tests, [1/178] in abinit tutorials

This variable controls the time (in atomic units) at which the external electric field is applied (see td_ef_type).

td_exp_order

Mnemonics: Time-Dependent EXPonential ORDER
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 4
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [5/1314] in all abinit tests, [1/178] in abinit tutorials

This variable controls the order of the Taylor expansion used to approximate the exponential of an operator in the propagator for RT-TDDFT. The default value of 4 is usually a good choice that ensures good stability and acceptable computation time.

td_propagator

Mnemonics: Time-Dependent PROPAGATOR
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [4/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls the propagation algorithm used to integrate the time-dependent Kohn-Sham equations in real-time TDDFT. At present only the exponential rule, td_propagator is 0, and the exponential mid-point rule, td_propagator is 1, propagators are implemented. Both are based on a Taylor expansion of the exponential of an operator which order is controlled by the td_exp_order parameter. In case of td_propagator equal to 1 the code uses a predictor-corrector scheme associated with two parameters td_scnmax and td_scthr.

td_prtstr

Mnemonics: Time-Dependent PRinT STRide
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [4/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls how often the code outputs various physical properties (DOS, occupations, current density etc.). The code will write these properties in files every td_prtstr time step.

td_restart

Mnemonics: Time-Dependent calculation RESTART
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver is 9
Added in version: 10

Test list (click to open). Rarely used, [6/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls wether we are restarting a RTTDDFT run. If td_restart is 0 the calculation starts from scratch, if it is set to 1 than ABINIT will read the file called TD_RESTART that contains some information in order to continue the previous RTTDDFT calculation.

td_scnmax

Mnemonics: Time-Dependent Self-Consistent NMAX
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 6
Only relevant if: optdriver is 9 and td_propagator is 1
Added in version: 10

Test list (click to open). Rarely used, [2/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls the maximum number of self-consistent corrector step in the predictor-corrector scheme (td_propagator equal to 1).

td_scthr

Mnemonics: Time-Dependent propagation Self-Consistent THReshold
Mentioned in topic(s): topic_RTTDDFT
Variable type: integer
Dimensions: scalar
Default value: 1e-07
Only relevant if: optdriver is 9 and td_propagator is 1
Added in version: 10

Test list (click to open). Rarely used, [2/1314] in all abinit tests, [0/178] in abinit tutorials

This variable controls the threshold used to define the convergence of the self-consistent predictor-corrector scheme (td_propagator equal to 1).