Section 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.

• Section path: CP2K_INPUT / NEGF / MIXING

• This section cannot be repeated.

• Subsections

  • none

• Keywords

  • SECTION_PARAMETERS
  • ALPHA
  • BETA
  • 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
  	&MIXING {Logical}
  	Controls the activation of the mixing procedure
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .TRUE.

  ALPHA
  	ALPHA {Real}
  	Fraction of new density to be included
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 4.00000000E-001

  BETA
  	BETA {Real}
  	Denominator parameter in Kerker damping introduced to suppress charge sloshing: rho_mix(g) =rho_in(g) + alpha*g^2/(g^2 + beta^2)*(rho_out(g)-rho_in(g))
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-001
  	Default unit: [bohr^-1]

  BROY_W0
  	BROY_W0 {Real}
  	w0 parameter used in Broyden mixing
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-002

  BROY_WMAX
  	BROY_WMAX {Real}
  	Without description, yet.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E+001

  BROY_WREF
  	BROY_WREF {Real}
  	Without description, yet.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+002

  GMIX_P
  	GMIX_P {Logical}
  	Activate the mixing of the density matrix, using the same mixing coefficient applied for the g-space mixing.
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  MAX_GVEC_EXP
  	MAX_GVEC_EXP {Real}
  	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.
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: -1.00000000E+000

  MAX_STEP
  	MAX_STEP {Real}
  	Upper bound for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-001

  METHOD
  	METHOD {Keyword}
  	Mixing method to be applied
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: DIRECT_P_MIXING
  	List of valid keywords: BROYDEN_MIXING Broyden mixing BROYDEN_MIXING_NEW Broyden mixing second version DIRECT_P_MIXING Direct mixing of new and old density matrices KERKER_MIXING Mixing of the potential in reciprocal space using the Kerker damping MULTISECANT_MIXING Multisecant scheme for mixing NONE No mixing is applied PULAY_MIXING Pulay mixing

  NBUFFER
  	NBUFFER {Integer}
  	Number of previous steps stored for the actual mixing scheme
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 4
  	Alias names for this keyword: NPULAY, NBROYDEN, NMULTISECANT

  NMIXING
  	NMIXING {Integer}
  	Minimal number of density mixing (should be greater than 0),before starting DIIS
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 2

  NSKIP
  	NSKIP {Integer}
  	Number of initial iteration for which the mixing is skipped
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0
  	Alias names for this keyword: NSKIP_MIXING

  N_SIMPLE_MIX
  	N_SIMPLE_MIX {Integer}
  	Number of kerker damping iterations before starting other mixing procedures
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0
  	Alias names for this keyword: NSIMPLEMIX

  PULAY_ALPHA
  	PULAY_ALPHA {Real}
  	Fraction of new density to be added to the Pulay expansion
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+000

  PULAY_BETA
  	PULAY_BETA {Real}
  	Fraction of residual contribution to be added to Pulay expansion
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+000

  REGULARIZATION
  	REGULARIZATION {Real}
  	Regularization parameter to stabilize the inversion of the residual matrix {Yn^t Yn} in the multisecant mixing scheme (noise)
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-005

  R_FACTOR
  	R_FACTOR {Real}
  	Control factor for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme
  	This keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-002