Section BECKE_CONSTRAINT

• Use the Becke weight population to enforce a charge/spin density constraint. The constraint is defined in the section ATOM_GROUP.

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

• This section cannot be repeated.

• This section cites the following reference: [Becke1988]

• Subsections

  • ATOM_GROUP
  • DUMMY_ATOMS
  • PROGRAM_RUN_INFO

• Keywords

  • ADJUST_SIZE
  • ATOMIC_CHARGES
  • ATOMIC_RADII
  • CAVITY_CONFINE
  • CAVITY_PRINT
  • CAVITY_RADIUS
  • CAVITY_SHAPE
  • CAVITY_USE_BOHR
  • CUTOFF_TYPE
  • ELEMENT_CUTOFF
  • EPS_CAVITY
  • FLIP_FRAGMENT_A
  • FLIP_FRAGMENT_B
  • FRAGMENT_A_FILE_NAME
  • FRAGMENT_A_SPIN_FILE
  • FRAGMENT_B_FILE_NAME
  • FRAGMENT_B_SPIN_FILE
  • GLOBAL_CUTOFF
  • IN_MEMORY
  • SHOULD_SKIP
  • STRENGTH
  • TARGET

• Keyword descriptions

  ADJUST_SIZE
  	ADJUST_SIZE {Logical}
  	Adjust Becke cell boundaries with atomic radii to generate a heteronuclear cutoff profile. These radii are defined with the keyword ATOMIC_RADII.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ATOMIC_CHARGES
  	ATOMIC_CHARGES {Logical}
  	Calculate atomic Becke charges (Z = Z_core - Z_becke). With fragment based constraints, charges are relative to the fragment reference state i.e. Z = Z_becke - Z_frag_reference. Note: if the number of atoms is greater than the default pw_pool max cache, calculation of atomic charges will prompt a warning 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.

  ATOMIC_RADII
  	ATOMIC_RADII {Real} ...
  	Defines atomic radii to generate a heteronuclear cutoff profile. Give one value per element in the same order as they appear in the input coordinates.
  	This keyword cannot be repeated and it expects a list of reals.
  	Default unit: [angstrom]

  CAVITY_CONFINE
  	CAVITY_CONFINE {Logical}
  	Activates Gaussian cavity confinement. The constraint is evaluated only inside the cavity. The cavity is formed by summing spherical Gaussians centered on the constraint atoms.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  CAVITY_PRINT
  	CAVITY_PRINT {Logical}
  	Print cavity in Gaussian cube file format. Currently, printing options are hardcoded.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  CAVITY_RADIUS
  	CAVITY_RADIUS {Real}
  	Radius parameter controlling the creation of Gaussian cavity confinement.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E+000
  	Default unit: [angstrom]

  CAVITY_SHAPE
  	CAVITY_SHAPE {Keyword}
  	Specifies the type of Gaussian cavity used.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: DEFAULT
  	List of valid keywords: COVALENT Use covalent radii to construct Gaussians. DEFAULT Use covalent radii (in angstrom) to construct Gaussians, but fixed 1.0_dp radius for elements with a radius larger than this value. SINGLE Single Gaussian for all atom types with radius given by CAVITY_RADIUS. USER Use user defined radii (keyword ATOMIC_RADII) to construct Gaussians. VDW Use van der Waals radii to construct Gaussians.

  CAVITY_USE_BOHR
  	CAVITY_USE_BOHR {Logical}
  	Convert the cavity radius from angstrom to bohr. This results in a larger confinement cavity than without unit conversion.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  CUTOFF_TYPE
  	CUTOFF_TYPE {Keyword}
  	Specifies the type of cutoff used when building the Becke weight function.
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: GLOBAL
  	List of valid keywords: ELEMENT Use a different value for all elements. Values read from ELEMENT_CUTOFF. GLOBAL Use a single value for all elements. Read from GLOBAL_CUTOFF.

  ELEMENT_CUTOFF
  	ELEMENT_CUTOFF {Real} ...
  	Defines element specific cutoffs to decide which atoms contribute to the weight function at each real space grid point. Give one value per element in the same order as they appear in the coordinates.
  	This keyword cannot be repeated and it expects a list of reals.
  	Default unit: [angstrom]

  EPS_CAVITY
  	EPS_CAVITY {Real}
  	Density threshold for cavity creation. Grid points where the Gaussian density falls below the threshold are ignored.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-006

  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

  GLOBAL_CUTOFF
  	GLOBAL_CUTOFF {Real}
  	Parameter used to select which atoms contribute to the weight function at each real space grid point.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.17506325E+000
  	Default unit: [angstrom]

  IN_MEMORY
  	IN_MEMORY {Logical}
  	Precompute gradients due to Becke constraint during initial formation of constraint and store them in memory. Useful in combination with confinement, memory intensive otherwise. 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.

  SHOULD_SKIP
  	SHOULD_SKIP {Logical}
  	If grid point is farther than GLOBAL_CUTOFF from all constraint atoms, move directly to next grid point, thus saving computational resources.
  	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 (Lagrangian 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