Section REAL_TIME_PROPAGATION

• Parameters needed to set up the real time propagation for the electron dynamics. This currently works only in the NVE ensemble.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / REAL_TIME_PROPAGATION

• This section cannot be repeated.

• This section cites the following references: [Andermatt2016] [Kunert2003]

• Subsections

  • PRINT

• Keywords

  • ACCURACY_REFINEMENT
  • APPLY_DELTA_PULSE
  • ASPC_ORDER
  • DELTA_PULSE_DIRECTION
  • DELTA_PULSE_SCALE
  • DENSITY_PROPAGATION
  • EPS_ITER
  • EXP_ACCURACY
  • HFX_BALANCE_IN_CORE
  • INITIAL_WFN
  • MAT_EXP
  • MAX_ITER
  • MCWEENY_EPS
  • MCWEENY_MAX_ITER
  • PERIODIC
  • PROPAGATOR
  • SC_CHECK_START

• Keyword descriptions

  ACCURACY_REFINEMENT
  	ACCURACY_REFINEMENT {Integer}
  	If using density propagation some parts should be calculated with a higher accuracy than the rest to reduce numerical noise. This factor determines by how much the filtering threshold is reduced for these calculations.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 100

  APPLY_DELTA_PULSE
  	APPLY_DELTA_PULSE {Logical}
  	Applies a delta kick to the initial wfn (only RTP for now - the EMD case is not yet implemented).
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ASPC_ORDER
  	ASPC_ORDER {Integer}
  	Speciefies how many steps will be used for extrapolation. One will be always used which is means X(t+dt)=X(t)
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 3

  DELTA_PULSE_DIRECTION
  	DELTA_PULSE_DIRECTION {Integer} {Integer} {Integer}
  	Direction of the applied electric field. The k vector is given as 2*Pi*[i,j,k]*inv(h_mat), which for PERIODIC .FALSE. yields exp(ikr) periodic with the unit cell, only if DELTA_PULSE_SCALE is set to unity. For an orthorhombic cell [1,0,0] yields [2*Pi/L_x,0,0]. For small cells, this results in a very large kick.
  	This keyword cannot be repeated and it expects precisely 3 integers.
  	Default values: 1 0 0

  DELTA_PULSE_SCALE
  	DELTA_PULSE_SCALE {Real}
  	Scale the k vector, which for PERIODIC .FALSE. results in exp(ikr) no longer being periodic with the unit cell. The norm of k is the strength of the applied electric field in atomic units.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-003

  DENSITY_PROPAGATION
  	DENSITY_PROPAGATION {Logical}
  	The density matrix is propagated instead of the molecular orbitals. This can allow a linear scaling simulation. The density matrix is filtered with the threshold based on the EPS_FILTER keyword from the LS_SCF section
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  EPS_ITER
  	EPS_ITER {Real}
  	Convergence criterion for the self consistent propagator loop.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-007

  EXP_ACCURACY
  	EXP_ACCURACY {Real}
  	Accuracy for the taylor and pade approximation. This is only an upper bound bound since the norm used for the guess is an upper bound for the needed one.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-009

  HFX_BALANCE_IN_CORE
  	HFX_BALANCE_IN_CORE {Logical}
  	If HFX is used, this keyword forces a redistribution/recalculation of the integrals, balanced with respect to the in core steps.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  INITIAL_WFN
  	INITIAL_WFN {Keyword}
  	Controls the initial WFN used for propagation.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: SCF_WFN
  	List of valid keywords: RESTART_WFN A wavefunction from a previous SCF is propagated. Especially useful, if electronic constraints or restraints are used in the previous calculation, since these do not work in the rtp scheme. RT_RESTART use the wavefunction of a real time propagation/ehrenfest run SCF_WFN An SCF run is performed to get the initial state.

  MAT_EXP
  	MAT_EXP {Keyword}
  	Which method should be used to calculate the exponential in the propagator. It is recommended to use BCH when employing density_propagation and ARNOLDI otherwise.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: ARNOLDI
  	List of valid keywords: ARNOLDI uses arnoldi subspace algorithm to compute exp(H)*MO directly, can't be used in combination with Crank Nicholson or density propagation BCH Uses a Baker-Campbell-Hausdorff expansion to propagate the density matrix, only works for density propagation PADE uses scaling and squaring together with the pade approximation TAYLOR exponential is evaluated using scaling and squaring in combination with a taylor expansion of the exponential.

  MAX_ITER
  	MAX_ITER {Integer}
  	Maximal number of iterations for the self consistent propagator loop.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 10

  MCWEENY_EPS
  	MCWEENY_EPS {Real}
  	Threshold after which McWeeny is terminated
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000

  MCWEENY_MAX_ITER
  	MCWEENY_MAX_ITER {Integer}
  	Determines the maximum amount of McWeeny steps used after each converged step in density propagation
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 1

  PERIODIC
  	PERIODIC {Logical}
  	Apply a delta-kick that is compatible with periodic boundary conditions for any value of DELTA_PULSE_SCALE. Uses perturbation theory for the preparation of the initial wfn. Note that the pulse is only applied when INITIAL_WFN is set to SCF_WFN, and not for restarts (RT_RESTART).
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .TRUE.

  PROPAGATOR
  	PROPAGATOR {Keyword}
  	Which propagator should be used for the orbitals
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: ETRS
  	List of valid keywords: CN Crank Nicholson propagator EM Exponential midpoint propagator ETRS enforced time reversible symmetry

  SC_CHECK_START
  	SC_CHECK_START {Integer}
  	Speciefies how many iteration steps will be done without a check for self consistency. Can save some time in big calculations.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0