# PARAMETER

Information on where to find DFTB parameters [Edit on GitHub]

## Keywords

- COORDINATION_CUTOFF

- D2_EXP_PRE

- D2_SCALING

- D3BJ_SCALING

- D3_SCALING

- DISPERSION_PARAMETER_FILE

- DISPERSION_RADIUS

- DISPERSION_TYPE

- HB_SR_PARAM

- PARAM_FILE_NAME

- PARAM_FILE_PATH

- SK_FILE

- UFF_FORCE_FIELD

## Keyword descriptions

COORDINATION_CUTOFF: real = 1.00000000E-006

  Usage: COORDINATION_CUTOFF

  Define cutoff for coordination number calculation [Edit on GitHub]

D2_EXP_PRE: real = 2.00000000E+000

  Usage: D2_EXP_PRE 2.0

  Exp prefactor for damping for the D2 dispersion method, [Edit on GitHub]

D2_SCALING: real = 1.00000000E+000

  Usage: D2_SCALING 1.0

  Scaling parameter for the D2 dispersion method, [Edit on GitHub]

D3BJ_SCALING: real[4] = 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000

  Usage: D3BJ_SCALING 1.0 1.0 1.0 1.0

  Scaling parameters (s6,a1,s8,a2) for the D3(BJ) dispersion method, [Edit on GitHub]

D3_SCALING: real[3] = 0.00000000E+000 0.00000000E+000 0.00000000E+000

  Usage: D3_SCALING 1.0 1.0 1.0

  Scaling parameters (s6,sr6,s8) for the D3 dispersion method, [Edit on GitHub]

DISPERSION_PARAMETER_FILE: string

  Usage: DISPERSION_PARAMETER_FILE filename

  Specify file that contains the atomic dispersion parameters for the D3 method [Edit on GitHub]

DISPERSION_RADIUS: real = 1.50000000E+001

  Usage: DISPERSION_RADIUS

  Define radius of dispersion interaction [Edit on GitHub]

DISPERSION_TYPE: enum = UFF

  Usage: DISPERSION_TYPE (UFF|D3|D3(BJ)|D2)

  Valid values:

  - `UFF` Uses the UFF force field for a pair potential dispersion correction.

  - `D3` Uses the Grimme D3 method (simplified) for a pair potential dispersion correction.

  - `D3(BJ)` Uses the Grimme D3 method (simplified) with Becke-Johnson attenuation.

  - `D2` Uses the Grimme D2 method for pair potential dispersion correction.

  Use dispersion correction of the specified type. Dispersion correction has to be switched on in the DFTB section. [Edit on GitHub]

HB_SR_PARAM: real = 4.00000000E+000

  Usage: HB_SR_PARAM {real}

  Uses a modified version for the GAMMA within the SCC-DFTB scheme, specifically tuned for hydrogen bonds. Specify the exponent used in the exponential. [Edit on GitHub]

PARAM_FILE_NAME: string

  Usage: PARAM_FILE_NAME filename

  Specify file that contains the names of Slater-Koster tables: A plain text file, each line has the format “ATOM1 ATOM2 filename.spl”. [Edit on GitHub]

PARAM_FILE_PATH: string = ./

  Usage: PARAM_FILE_PATH pathname

  Specify the directory with the DFTB parameter files. Used in combination with the filenames specified in the file given in PARAM_FILE_NAME. [Edit on GitHub]

SK_FILE: string[3]

  Keyword can be repeated.

  Usage: SK_FILE a1 a2 filename

  Define parameter file for atom pair [Edit on GitHub]

UFF_FORCE_FIELD: string

  Usage: UFF_FORCE_FIELD filename

  Name of file with UFF parameters that will be used for the dispersion correction. Needs to be specified when DISPERSION==.TRUE., otherwise cp2k crashes with a Segmentation Fault. [Edit on GitHub]