Section CDFT

• Parameters needed to set up a constrained DFT calculation. Each repetition of the ATOM_GROUP section defines a new constraint. The constraint(s) is (are) converged in a separate external SCF loop with settings read from the OUTER_SCF section. Supported constraints: Becke and Gaussian Hirshfeld (partial).

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / QS / CDFT

• This section cannot be repeated.

• This section cites the following references: [Holmberg2017] [Holmberg2018]

• Subsections

  • ATOM_GROUP
  • BECKE_CONSTRAINT
  • DUMMY_ATOMS
  • HIRSHFELD_CONSTRAINT
  • OUTER_SCF
  • PROGRAM_RUN_INFO

• Keywords

  • ATOMIC_CHARGES
  • COUNTER
  • FLIP_FRAGMENT_A
  • FLIP_FRAGMENT_B
  • FRAGMENT_A_FILE_NAME
  • FRAGMENT_A_SPIN_FILE
  • FRAGMENT_B_FILE_NAME
  • FRAGMENT_B_SPIN_FILE
  • IN_MEMORY
  • MAX_REUSE
  • PRECOND_FREQ
  • PURGE_FREQ
  • PURGE_HISTORY
  • PURGE_OFFSET
  • REUSE_PRECOND
  • STRENGTH
  • TARGET
  • TYPE_OF_CONSTRAINT

• Keyword descriptions

  ATOMIC_CHARGES
  	ATOMIC_CHARGES {Logical}
  	Calculate atomic CDFT charges with selected weight function (Z = Z_core - Z_CDFT). With fragment based constraints, charges are relative to the fragment reference state i.e. Z = Z_CDFT - Z_frag_reference. Note: if the number of atoms is greater than the default pw_pool max cache, calculation of atomic CDFT charges will prompt harmless warnings during deallocation of atomic grids.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  COUNTER
  	COUNTER {Integer}
  	A counter to track the total number of energy evaluations. Needed by some optimizers to print information. Useful mainly for restarts.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0

  FLIP_FRAGMENT_A
  	FLIP_FRAGMENT_A {Logical}
  	Logical which determines if the reference spin difference density (rho_alpha-rho_beta) for fragment A should be flipped. With default (off) value, the fragment is constrained to have more alpha than beta electrons if the isolated fragment has unpaired electrons. Useful in conjunction with FLIP_FRAGMENT_B.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  FLIP_FRAGMENT_B
  	FLIP_FRAGMENT_B {Logical}
  	Logical which determines if the reference spin difference density (rho_alpha-rho_beta) for fragment B should be flipped. With default (off) value, the fragment is constrained to have more alpha than beta electrons if the isolated fragment has unpaired electrons. Useful in conjunction with FLIP_FRAGMENT_A.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  FRAGMENT_A_FILE_NAME
  	FRAGMENT_A_FILE_NAME {String}
  	Name of the reference total electron density cube file for fragment A. May include a path. The reference electron density needs to be outputted on the same grid as the full system (same cutoff and cell, output stride 1).
  	This keyword cannot be repeated and it expects precisely one string.
  	Default value: fragment_a.cube
  	Alias names for this keyword: FRAGMENT_A_FILE

  FRAGMENT_A_SPIN_FILE
  	FRAGMENT_A_SPIN_FILE {String}
  	Name of the reference spin density cube file for fragment A. May include a path. The reference spin density needs to be outputted on the same grid as the full system (same cutoff and cell, output stride 1).
  	This keyword cannot be repeated and it expects precisely one string.
  	Default value: fragment_a_spin.cube
  	Alias names for this keyword: FRAGMENT_A_SPIN_FILE_NAME

  FRAGMENT_B_FILE_NAME
  	FRAGMENT_B_FILE_NAME {String}
  	Name of the reference total electron density cube file for fragment B. May include a path. The reference electron density needs to be outputted on the same grid as the full system (same cutoff and cell, output stride 1).
  	This keyword cannot be repeated and it expects precisely one string.
  	Default value: fragment_b.cube
  	Alias names for this keyword: FRAGMENT_B_FILE

  FRAGMENT_B_SPIN_FILE
  	FRAGMENT_B_SPIN_FILE {String}
  	Name of the reference spin density cube file for fragment B. May include a path. The reference spin density needs to be outputted on the same grid as the full system (same cutoff and cell, output stride 1).
  	This keyword cannot be repeated and it expects precisely one string.
  	Default value: fragment_b_spin.cube
  	Alias names for this keyword: FRAGMENT_B_SPIN_FILE_NAME

  IN_MEMORY
  	IN_MEMORY {Logical}
  	Precompute gradients due to constraint during initial formation of constraint and store them in memory. Does nothing if forces are not calculated.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  MAX_REUSE
  	MAX_REUSE {Integer}
  	Determines how many times a previously built preconditioner can be reused.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0

  PRECOND_FREQ
  	PRECOND_FREQ {Integer}
  	See REUSE_PRECOND.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0

  PURGE_FREQ
  	PURGE_FREQ {Integer}
  	See PURGE_HISTORY.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 1

  PURGE_HISTORY
  	PURGE_HISTORY {Logical}
  	Purge wavefunction and constraint history to improve SCF convergence during MD. Counts how often the convergence of the first CDFT SCF iteration takes 2 or more outer SCF iterations and purges the history if the counter exceeds PURGE_FREQ, and PURGE_OFFSET MD steps have passed since the last purge. The counter is zeroed after each purge.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  PURGE_OFFSET
  	PURGE_OFFSET {Integer}
  	See PURGE_HISTORY.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 1

  REUSE_PRECOND
  	REUSE_PRECOND {Logical}
  	Reuse a previously built OT preconditioner between subsequent CDFT SCF iterations if the inner OT SCF loop converged in PRECOND_FREQ steps or less. Intended mainly for MD simulations with the FULL_ALL preconditioner to speed up the final iterations of the CDFT SCF loop.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  STRENGTH
  	STRENGTH {Real} ...
  	Constraint force constants (Lagrange multipliers). Give one value per constraint group.
  	This keyword cannot be repeated and it expects a list of reals.
  	Default value: 0.00000000E+000

  TARGET
  	TARGET {Real} ...
  	Constraint target values. Give one value per constraint group. The target value is the desired number of valence electrons, spin moment, or the number of alpha or beta electrons on the atoms that define the constraint, suitably multiplied by atomic coefficients in case a relative constraint between two sets of atoms is employed. Note that core charges are not subtracted from the target value.
  	This keyword cannot be repeated and it expects a list of reals.
  	Default value: 0.00000000E+000

  TYPE_OF_CONSTRAINT
  	TYPE_OF_CONSTRAINT {Keyword}
  	Specifies the type of constraint used.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: NONE
  	List of valid keywords: BECKE Becke constraint. Requires corresponding section. HIRSHFELD Gaussian Hirshfeld constraint. Partial implementation: no forces. Requires corresponding section. Not as extensively tested. NONE No constraint (disables section).
  	This keyword cites the following reference: [Becke1988b]