EXTERNAL_POTENTIAL
Section controlling the presence of an electrostatic external potential dependent on the atomic positions (X,Y,Z). As the external potential is currently applied via a grid, it only works with DFT based methods (GPW/GAPW) that already use a grid-based approach to solve the Poisson equation. Not to be confused with other similar sections:
FORCE_EVAL/EXTERNAL_POTENTIAL, which is applicable to general force methods and is not grid-based;
FORCE_EVAL/DFT/EFIELD, which is for finite, time-dependent electric field in DFT;
FORCE_EVAL/DFT/PERIODIC_EFIELD, which is for finite periodic electric field using the Berry phase approach in DFT.
The following 3 symbol(s) will be reserved as the variable(s) to be substituted for internal evaluation: X, Y, Z. They cannot be used as parameters.
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Subsections
Keywords
Keyword descriptions
DX
Type: real
Default: 1.00000000E-001 [bohr]
Usage: DX <REAL>
Description: Parameter used for computing the derivative with the Ridders’ method. [Edit on GitHub]
ERROR_LIMIT
Type: real
Default: 1.00000000E-012
Usage: ERROR_LIMIT <REAL>
Description: Checks that the error in computing the derivative is not larger than the value set; in case error is larger a warning message is printed. [Edit on GitHub]
FUNCTION
Type: string
Usage: FUNCTION A*X+B*(2/(1+EXP(-0.001*Y))-1)
Description: Specifies a functional form. The maximum length is 1024 characters. Mathematical Operators recognized are +, -, *, /, ^ or alternatively **, whereas symbols for brackets must be (). The function parser recognizes the Fortran 90 intrinsic functions abs, min, max, exp, log10, log, sqrt, sinh, cosh, tanh, sin, cos, tan, asin, acos, atan2, atan, erf, erfc. Parsing for intrinsic functions is not case sensitive.
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PARAMETERS
Type: string[ ]
Repeatable: yes
Usage: PARAMETERS A B
Description: Defines the symbols for the parameter(s) in the functional form, delimited by whitespaces. Symbols are case sensitive and each is at most 80 characters long. [Edit on GitHub]
READ_FROM_CUBE
Type: logical
Default: F
Lone keyword: T
Usage: READ_FROM_CUBE T
Description: Switch for reading the external potential from file pot.cube. The values of the potential must be on the grid points of the realspace grid. Whitespace-separated cube values are accepted. If adjacent values are written without whitespace, each value must occupy a 13-character E13.5 field. [Edit on GitHub]
SCALING_FACTOR
Type: real
Default: 1.00000000E+000
Usage: SCALING_FACTOR <REAL>
Description: A factor for scaling the the external potential that is read from file. The value of the potential at each grid point is multiplied by this factor. [Edit on GitHub]
STATIC
Type: logical
Default: T
Lone keyword: T
Usage: STATIC T
Description: Specifies the external potential as STATIC or time dependent. At the moment only static potentials are implemented. [Edit on GitHub]
UNITS
Type: string[ ]
Repeatable: yes
Usage: UNITS eV*angstrom^-1 angstrom
Description: Optionally, defines CP2K unit string for each of the given parameter value(s). A valid CP2K unit string is one of the strings that is listed under the References/Units section of the CP2K manual, or a combination of multiple of these strings with *, / and ^. It is assumed that the corresponding parameter value is specified in this unit which needs to be converted first to the internal unit during input parsing. Note that the meaningfulness of the unit is not checked. If omitted, all values will be treated as already in the internal unit and used literally.
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VALUES
Type: real[ ]
Default: [internal_cp2k]
Repeatable: yes
Usage: VALUES 50 1.0E+2
Description: Defines the value(s) of the parameter in the functional form. [Edit on GitHub]