MIXING

Define type and parameters for mixing procedures to be applied to the density matrix. Normally, only one type of mixing method should be accepted. The mixing procedures activated by this section are only active for diagonalization methods and linear scaling SCF, i.e. not with minimization methods based on OT. [Edit on GitHub]

Keywords

• SECTION_PARAMETERS

• ALPHA

• ALPHA_MAG

• BETA

• BETA_MAG

• BROY_W0

• BROY_WMAX

• BROY_WREF

• GMIX_P

• MAX_GVEC_EXP

• MAX_STEP

• METHOD

• NBUFFER

• NMIXING

• NSKIP

• N_SIMPLE_MIX

• PULAY_ALPHA

• PULAY_BETA

• REGULARIZATION

• R_FACTOR

Keyword descriptions

SECTION_PARAMETERS: logical = T

Lone keyword: T

Usage: &MIXING ON

Controls the activation of the mixing procedure [Edit on GitHub]

ALPHA: real = 4.00000000E-001

Usage: ALPHA 0.2

Fraction of new density to be included [Edit on GitHub]

ALPHA_MAG: real = -1.00000000E+000

Usage: ALPHA_MAG 0.8

Fraction of new magnetization density to be included (for spin-polarized calculations, ispin=2 channel after rho_total/m transform). A negative value (default) means: use the same value as ALPHA. For magnetic transition-metal systems, a larger value (e.g. 0.8-1.6) than ALPHA often improves convergence. [Edit on GitHub]

BETA: real = 5.00000000E-001 [bohr^-1]

Usage: BETA 1.5

Denominator parameter in Kerker damping introduced to suppress charge sloshing: rho_mix(g) = rho_in(g) + alphag^2/(g^2 + beta^2)(rho_out(g)-rho_in(g)) [Edit on GitHub]

BETA_MAG: real = -1.00000000E+000 [bohr^-1]

Usage: BETA_MAG 0.0

Kerker damping parameter for the magnetization channel (for spin-polarized calculations). A negative value (default) means: use the same value as BETA. Set to 0.0 to disable Kerker screening on the magnetization density, which avoids suppression of long-range magnetic order formation in transition-metal systems. [Edit on GitHub]

BROY_W0: real = 1.00000000E-002

Usage: BROY_W0 0.03

Regularization weight used in Broyden mixing. For the original BROYDEN_MIXING method this is the constant diagonal regularization of the small Broyden system. For MODIFIED_BROYDEN_MIXING it is the corresponding diagonal regularization of the dynamically weighted Broyden system. The default follows tblite. [Edit on GitHub]

BROY_WMAX: real = 1.00000000E+005

Usage: BROY_WMAX 100000.0

Upper bound for the dynamic residual weight. This keyword is only used by MODIFIED_BROYDEN_MIXING; the original BROYDEN_MIXING path is unchanged. The lower bound is fixed to 1.0. The default follows tblite. [Edit on GitHub]

BROY_WREF: real = 1.00000000E-002

Usage: BROY_WREF 0.01

Reference factor for the dynamic residual weight. This keyword is only used by MODIFIED_BROYDEN_MIXING; the original BROYDEN_MIXING path is unchanged. The effective history weight is proportional to BROY_WREF divided by the residual norm, clipped to the interval [1, BROY_WMAX]. The default follows tblite. [Edit on GitHub]

GMIX_P: logical = F

Lone keyword: T

Usage: GMIX_P

Activate the mixing of the density matrix, using the same mixing coefficient applied for the g-space mixing. [Edit on GitHub]

MAX_GVEC_EXP: real = -1.00000000E+000

Usage: MAX_GVEC_EXP 3.

Restricts the G-space mixing to lower part of G-vector spectrum, up to a G0, by assigning the exponent of the Gaussian that can be represented by vectors smaller than G0 within a certain accuracy. [Edit on GitHub]

MAX_STEP: real = 1.00000000E-001

Usage: MAX_STEP .2

Upper bound for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme [Edit on GitHub]

METHOD: enum = DIRECT_P_MIXING

Usage: METHOD KERKER_MIXING

Valid values:

• NONE No mixing is applied

• DIRECT_P_MIXING Direct mixing of new and old density matrices

• KERKER_MIXING Mixing of the potential in reciprocal space using the Kerker damping

• PULAY_MIXING Pulay mixing

• BROYDEN_MIXING Original CP2K Broyden mixing with a constant BROY_W0 regularization

• MODIFIED_BROYDEN_MIXING Modified Broyden mixing with dynamic residual weights controlled by BROY_W0, BROY_WREF, and BROY_WMAX

• MULTISECANT_MIXING Multisecant scheme for mixing

Mixing method to be applied [Edit on GitHub]

NBUFFER: integer = 4

Aliases: NPULAY ,NBROYDEN ,NMULTISECANT

Usage: NBUFFER 2

Number of previous steps stored for the actual mixing scheme [Edit on GitHub]

NMIXING: integer = 2

Usage: NMIXING 1

Minimal number of density mixing (should be greater than 0), before starting DIIS [Edit on GitHub]

NSKIP: integer = 0

Aliases: NSKIP_MIXING

Usage: NSKIP 10

Number of initial iteration for which the mixing is skipped [Edit on GitHub]

N_SIMPLE_MIX: integer = 0

Aliases: NSIMPLEMIX

Usage: NSIMPLEMIX

Number of kerker damping iterations before starting other mixing procedures [Edit on GitHub]

PULAY_ALPHA: real = 0.00000000E+000

Usage: PULAY_ALPHA 0.2

Fraction of new density to be added to the Pulay expansion [Edit on GitHub]

PULAY_BETA: real = 1.00000000E+000

Usage: PULAY_BETA 0.2

Fraction of residual contribution to be added to Pulay expansion [Edit on GitHub]

REGULARIZATION: real = 1.00000000E-005

Usage: REGULARIZATION 0.000001

Regularization parameter to stabilize the inversion of the residual matrix {Yn^t Yn} in the multisecant mixing scheme (noise) [Edit on GitHub]

R_FACTOR: real = 5.00000000E-002

Usage: R_FACTOR .12

Control factor for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme [Edit on GitHub]