Section MIXING

• Define type and parameters for mixingprocedures 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, i.e. not with minimization methods based on OT.

• Section path: CP2K_INPUT / FORCE_EVAL / DFT / XAS / MIXING

• This section cannot be repeated and can be optional.

• Subsections

  • none

• Keywords

  • SECTION_PARAMETERS
  • ALPHA
  • BETA
  • BROY_W0
  • BROY_WMAX
  • BROY_WREF
  • KERKER_MIN
  • MAX_GVEC_EXP
  • MAX_STEP
  • METHOD
  • NBUFFER
  • NMIXING
  • NSKIP
  • N_SIMPLE_MIX
  • PULAY_ALPHA
  • PULAY_BETA
  • REGULARIZATION
  • R_FACTOR

• Keyword descriptions

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

  ALPHA
  	ALPHA 0.2
  	Fraction of new density to be included
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 4.00000000E-01

  BETA
  	BETA 1.5
  	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 optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-01
  	Default unit: [bohr^-1]

  BROY_W0
  	BROY_W0 0.03
  	w0 parameter used in Broyden mixing
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-02

  BROY_WMAX
  	BROY_WMAX 10.0
  	Without description, yet.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 3.00000000E+01

  BROY_WREF
  	BROY_WREF 0.2
  	Without description, yet.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+02

  KERKER_MIN
  	KERKER_MIN 0.05
  	Minimal Kerker damping factor: MAX(g^2/(g^2 + beta^2),KERKER_MIN)
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-01

  MAX_GVEC_EXP
  	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.
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: -1.00000000E+00

  MAX_STEP
  	MAX_STEP .2
  	Upper bound for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-01

  METHOD
  	METHOD KERKER_MIXING
  	Mixing method to be applied
  	This optional 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 2
  	Number of previous steps stored for the actual mixing scheme
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 4
  	Alias names for this keyword: NPULAY, NBROYDEN, NMULTISECANT

  NMIXING
  	NMIXING 1
  	Minimal number of density mixing (should be greater than 0),before starting DIIS
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 2

  NSKIP
  	NSKIP 10
  	Number of initial iteration for which the mixing is skipped
  	This optional keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0
  	Alias names for this keyword: NSKIP_MIXING

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

  PULAY_ALPHA
  	PULAY_ALPHA 0.2
  	Fraction of new density to be added to the Pulay expansion
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 0.00000000E+00

  PULAY_BETA
  	PULAY_BETA 0.2
  	Fraction of residual contribution to be added to Pulay expansion
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E+00

  REGULARIZATION
  	REGULARIZATION 0.000001
  	Regularization parameter to stabilize the inversion of the residual matrix {Yn^t Yn} in the multisecant mixing scheme (noise)
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 1.00000000E-05

  R_FACTOR
  	R_FACTOR .12
  	Control factor for the magnitude of the unpredicted step size in the update by the multisecant mixing scheme
  	This optional keyword cannot be repeated and it expects precisely one real.
  	Default value: 5.00000000E-02