Section CDFT_OPT

• Parameters controlling optimization methods that are compatible only with CDFT based constraints (i.e. CDFT SCF is active). Specifically, the control parameters for the Broyden and Newton optimizers are defined in this section.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / XAS / SCF / OUTER_SCF / CDFT_OPT

• This section cannot be repeated.

• Subsections

  • none

• Keywords

  • BROYDEN_TYPE
  • CONTINUE_LS
  • FACTOR_LS
  • JACOBIAN_FREQ
  • JACOBIAN_RESTART
  • JACOBIAN_STEP
  • JACOBIAN_TYPE
  • JACOBIAN_VECTOR
  • MAX_LS

• Keyword descriptions

  BROYDEN_TYPE
  	BROYDEN_TYPE {Keyword}
  	Specifies the Broyden optimizer variant to use.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: BT1
  	List of valid keywords: BT1 Broyden's first method, also known as the good method. The initial Jacobian is built from MD history if available. Otherwise switches to SD for one SCF iteration until a Jacobian can be built from the SCF history. BT1_EXPLICIT Same as BT1, but computes the explicit Jacobian with finite differences. Requires a CDFT SCF procedure to be active. BT1_EXPLICIT_LS Same as BT1_EXPLICIT, but uses backtracking line search for optimizing the step size. BT1_LS Same as BT1, but uses backtracking line search for optimizing the step size (see optimizer NEWTON_LS). BT2 Same as BT1, but uses Broyden's second method, also known as the bad method. BT2_EXPLICIT Same as BT1_EXPLICIT, but using Broyden's second method. BT2_EXPLICIT_LS Same as BT2_EXPLICIT, but uses backtracking line search for optimizing the step size. BT2_LS Same as BT2, but uses backtracking line search for optimizing the step size.

  CONTINUE_LS
  	CONTINUE_LS {Logical}
  	Continue backtracking line search until MAX_LS steps are reached or the norm of the CDFT gradient no longer decreases. Default (false) behavior exits the line search procedure on the first step that the gradient decreases.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  FACTOR_LS
  	FACTOR_LS {Real}
  	Control parameter for backtracking line search. The step size is reduced by this factor on every line search iteration. Value must be between 0 and 1 (exclusive).
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-001

  JACOBIAN_FREQ
  	JACOBIAN_FREQ {Integer} {Integer}
  	Defines parameters that control how often the explicit Jacobian is built, which is needed by some optimizers. Expects two values. The first value determines how many consecutive CDFT SCF iterations should skip a rebuild, whereas the latter how many MD steps. The values can be zero (meaning never rebuild) or positive. Both values cannot be zero.
  	This keyword cannot be repeated and it expects precisely 2 integers.
  	Default values: 1 1

  JACOBIAN_RESTART
  	JACOBIAN_RESTART {Logical}
  	Restart the inverse Jacobian using the vector defined with keyword JACOBIAN_VECTOR.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  JACOBIAN_STEP
  	JACOBIAN_STEP {Real} ...
  	Step size to use in the calculation of the inverse Jacobian with finite differences. Expects one value for all constraints, or one value per constraint.
  	This keyword cannot be repeated and it expects a list of reals.
  	Default value: 5.00000000E-003

  JACOBIAN_TYPE
  	JACOBIAN_TYPE {Keyword}
  	Finite difference method used to calculate the inverse Jacobian needed by some optimizers. Compatible only with CDFT constraints.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: FD1
  	List of valid keywords: FD1 First order forward difference (one extra energy evaluation per constraint). FD1_BACKWARD First order backward difference (one extra energy evaluation per constraint). FD1_CENTRAL First order central difference (two extra energy evaluations per constraint). FD2 Second order forward difference (two extra energy evaluations per constraint). FD2_BACKWARD Second order backward difference (two extra energy evaluations per constraint).

  JACOBIAN_VECTOR
  	JACOBIAN_VECTOR {Real} ...
  	Defines the inverse Jacobian matrix. Useful for restarting calculations. Expects n^2 values where n is the total number of constraints. The matrix should be given in row major order.
  	This keyword cannot be repeated and it expects a list of reals.

  MAX_LS
  	MAX_LS {Integer}
  	The maximum number of backtracking line search steps to perform.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 5