QMMM

References: Laino2005, Laino2006

Controls QM/MM calculations, including mechanical, electrostatic, Gaussian-expanded, and periodic embedding options. [Edit on GitHub]

Subsections

Keywords

Keyword descriptions

CENTER

Type: enum
Default: EVERY_STEP
Usage: center (EVERY_STEP|SETUP_ONLY|NEVER)

Description: This keyword sets when the QM system is automatically centered. Default is EVERY_STEP.

Valid values:

  • EVERY_STEP Re-center every step

  • SETUP_ONLY Center at first step only

  • NEVER Never center

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CENTER_GRID

Type: logical
Default: F
Usage: CENTER_GRID LOGICAL

Description: This keyword specifies whether the QM system is centered in units of the grid spacing.

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CENTER_TYPE

Type: enum
Default: MAX_MINUS_MIN
Usage: center_type (MAX_MINUS_MIN|PBC_AWARE_MAX_MINUS_MIN)

Description: This keyword specifies how to do the QM system centering.

Valid values:

  • MAX_MINUS_MIN Center of box defined by maximum coordinate minus minimum coordinate

  • PBC_AWARE_MAX_MINUS_MIN PBC-aware centering (useful for &QMMM&FORCE_MIXING)

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DELTA_CHARGE

Type: integer
Default: 0
Usage: DELTA_CHARGE q

Description: Additional net charge relative to that specified in DFT section. Used automatically by force mixing

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EPS_MM_RSPACE

Type: real
Default: 1.00000000E-010
Usage: eps_mm_rspace real

Description: Set the threshold for the collocation of the GEEP gaussian functions. this keyword affects only the GAUSS E_COUPLING.

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E_COUPL

Type: enum
Default: NONE
Aliases: QMMM_COUPLING, ECOUPL
Usage: E_COUPL GAUSS

Description: Selects the QM-MM coupling model used for the electrostatic interaction.

Valid values:

  • NONE Mechanical coupling (i.e. classical point charge based)

  • COULOMB Using analytical 1/r potential (Coulomb) - not available for GPW/GAPW

  • GAUSS Using fast Gaussian expansion of the electrostatic potential (Erf(r/rc)/r) - not available for DFTB.

  • S-WAVE Using fast Gaussian expansion of the s-wave electrostatic potential

  • POINT_CHARGE Using quantum mechanics derived point charges interacting with MM charges

Mentions: ⭐QM/MM with Built-in Force Field

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INITIAL_TRANSLATION_VECTOR

Type: real[3]
Default: 0.00000000E+000 0.00000000E+000 0.00000000E+000
Usage: initial_translation_vector

Description: This keyword specify the initial translation vector to be applied to the system.

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MM_POTENTIAL_FILE_NAME

Type: string
Default: MM_POTENTIAL
Usage: MM_POTENTIAL_FILE_NAME {filename}

Description: Name of the file containing the potential expansion in gaussians. See the USE_GEEP_LIB keyword.

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NOCOMPATIBILITY

Type: logical
Default: F
Lone keyword: T
Usage: nocompatibility LOGICAL

Description: This keyword disables the compatibility of QM/MM potential between CPMD and CP2K implementations. The compatibility is achieved using an MM potential of the form: Erf[x/rc]/x + (1/rc -2/(pi^1/2*rc))*Exp[-(x/rc)^2]. This keyword has effect only selecting GAUSS E_COUPLING type.

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PARALLEL_SCHEME

Type: enum
Default: ATOM
Usage: parallel_scheme (ATOM|GRID)

Description: Chooses the parallel_scheme for the long range Potential

Valid values:

  • ATOM parallelizes on atoms. grids replicated. Replication of the grids can be quite expensive memory wise if running on a system with limited memory per core. The grid option may be preferred in this case.

  • GRID parallelizes on grid slices. atoms replicated.

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SPHERICAL_CUTOFF

Type: real[2]
Default: -5.29177209E-001 0.00000000E+000 [angstrom]
Usage: SPHERICAL_CUTOFF

Description: Set the spherical cutoff for the QMMM electrostatic interaction. This acts like a charge multiplicative factor dependent on cutoff. For MM atoms farther than the SPHERICAL_CUTOFF(1) their charge is zero. The switch is performed with a smooth function: 0.5*(1-TANH((r-[SPH_CUT(1)-20*SPH_CUT(2)])/(SPH_CUT(2)))). Two values are required: the first one is the distance cutoff. The second one controls the stiffness of the smoothing.

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USE_GEEP_LIB

Type: integer
Default: 0
Usage: use_geep_lib INTEGER

Description: This keyword enables the use of the internal GEEP library to generate the gaussian expansion of the MM potential. Using this keyword there’s no need to provide the MM_POTENTIAL_FILENAME. It expects a number from 2 to 15 (the number of gaussian functions to be used in the expansion.

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