Section FORCE_MIXING

• This section enables and defines parameters for force-mixing based QM/MM, which actually does two conventional QM/MM calculations, on a small and a large QM region, and combines the MM forces from one and QM forces from the other to create a complete set of forces. Energy is not conserved (although the QM/MM energy from the large QM region calculation is reported) so a proper thermostat (i.e. massive, and able to handle dissipation, such as Adaptive Langevin (AD_LANGEVIN)) must be used. For some propagation algorithms (NVT and REFTRAJ MD ensembles) algorithm is adaptive, including molecules hysteretically based on their instantaneous distance from the core region. Information on core/QM/buffer labels can be written in PDB file using MOTION&PRINT&FORCE_MIXING_LABELS. Will fail if calculation requires a meaningfull stress, or an energy that is consistent with the forces. For GEO_OPT this means only MOTION&GEO_OPT&TYPE CG, MOTION&GEO_OPT&CG&LINE_SEARCH&TYPE 2PNT, and MOTION&GEO_OPT&CG&LINE_SEARCH&2PNT&LINMIN_GRAD_ONLY T

• Section path: CP2K_INPUT / FORCE_EVAL / QMMM / FORCE_MIXING

• This section cannot be repeated.

• This section cites the following references: [Bernstein2009] [Bernstein2012]

• Subsections

  • BUFFER_LINKS
  • BUFFER_NON_ADAPTIVE
  • PRINT
  • QM_NON_ADAPTIVE
  • RESTART_INFO

• Keywords

  • SECTION_PARAMETERS
  • ADAPTIVE_EXCLUDE_MOLECULES
  • EXTENDED_DELTA_CHARGE
  • MAX_N_QM
  • MOMENTUM_CONSERVATION_REGION
  • MOMENTUM_CONSERVATION_TYPE
  • QM_EXTENDED_SEED_IS_ONLY_CORE_LIST
  • QM_KIND_ELEMENT_MAPPING
  • R_BUF
  • R_CORE
  • R_QM

• Keyword descriptions

  SECTION_PARAMETERS
  	&FORCE_MIXING {Logical}
  	Enables force-mixing
  	This keyword cannot be repeated and it expects precisely one logical.
  	The lone keyword behaves as a switch to .TRUE.
  	Default value: .FALSE.

  ADAPTIVE_EXCLUDE_MOLECULES
  	ADAPTIVE_EXCLUDE_MOLECULES {Word} ...
  	List of molecule names to exclude from adaptive regions (e.g. big things like proteins)
  	This keyword cannot be repeated and it expects a list of words.

  EXTENDED_DELTA_CHARGE
  	EXTENDED_DELTA_CHARGE {Integer}
  	Additional net charge in extended region relative to core (core charge is specified in DFT section, as usual for a convetional QM/MM calculation)
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 0

  MAX_N_QM
  	MAX_N_QM {Integer}
  	Maximum number of QM atoms, for detection of runaway adaptive selection.
  	This keyword cannot be repeated and it expects precisely one integer.
  	Default value: 300

  MOMENTUM_CONSERVATION_REGION
  	MOMENTUM_CONSERVATION_REGION {Keyword}
  	Region to apply correction force to for momentum conservation
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: QM
  	List of valid keywords: BUFFER Apply to QM+buffer regions CORE Apply to QM core region QM Apply to full QM (dynamics) region

  MOMENTUM_CONSERVATION_TYPE
  	MOMENTUM_CONSERVATION_TYPE {Keyword}
  	How to apply force to get momentum conservation
  	This keyword cannot be repeated and it expects precisely one keyword.
  	Default value: EQUAL_A
  	List of valid keywords: EQUAL_A Equal acceleration on each atom EQUAL_F Equal force on each atom NONE No momentum conservation

  QM_EXTENDED_SEED_IS_ONLY_CORE_LIST
  	QM_EXTENDED_SEED_IS_ONLY_CORE_LIST {Logical}
  	Makes the extended QM zone be defined hysterestically by distance from QM core list (i.e. atoms specified explicitly by user) instead of from full QM core region (specified by user + hysteretic selection + unbreakable bonds)
  	This keyword cannot be repeated and it expects precisely one logical.
  	Default value: .FALSE.

  QM_KIND_ELEMENT_MAPPING
  	QM_KIND_ELEMENT_MAPPING {Word} {Word}
  	Mapping from elements to QM_KINDs for adaptively included atoms.
  	This keyword can be repeated and it expects precisely 2 words.

  R_BUF
  	R_BUF {Real} {Real}
  	Specify the inner and outer radii of buffer region. All atoms within this distance (hysteretically) of any QM atoms will be buffer atoms in the force-mixing calculation.
  	This keyword cannot be repeated and it expects precisely 2 reals.
  	Default values: 5.00000000E-01 1.00000000E+00
  	Default unit: [angstrom]

  R_CORE
  	R_CORE {Real} {Real}
  	Specify the inner and outer radii of core QM region. All molecules with any atoms within this distance (hysteretically) of any atoms specified as QM in enclosing QM/MM section will be core QM atoms in the force-mixing calculation.
  	This keyword cannot be repeated and it expects precisely 2 reals.
  	Default values: 0.00000000E+00 0.00000000E+00
  	Default unit: [angstrom]

  R_QM
  	R_QM {Real} {Real}
  	Specify the inner and outer radii of QM dynamics region. All molecules with atoms within this distance (hysteretically) of any atoms in core will follow QM dynamics in the force-mixing calculation.
  	This keyword cannot be repeated and it expects precisely 2 reals.
  	Default values: 5.00000000E-01 1.00000000E+00
  	Default unit: [angstrom]