CELL_REF

Input parameters needed to set up the reference cell for FORCE_EVAL/SUBSYS/CELL. This option can be used to keep the FFT grid fixed while running a cell optimization or NpT molecular dynamics. Check the &CELL section for further details. [Edit on GitHub]

Keywords

Keyword descriptions

A

Type: real[3]
Default: [angstrom]
Usage: A 10.000 0.000 0.000

Description: Specify the Cartesian components for the cell vector A. This defines the first column of the h matrix. Ignored if the keywords ABC or CELL_FILE_NAME are used.

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ABC

Type: real[3]
Default: [angstrom]
Usage: ABC 10.000 10.000 10.000

Description: Specify the lengths of the cell vectors A, B, and C, which defines the diagonal elements of h matrix for an orthorhombic cell. For non-orthorhombic cells it is possible either to specify the angles ALPHA, BETA, GAMMA via ALPHA_BETA_GAMMA keyword or alternatively use the keywords A, B, and C. The convention is that A lies along the X-axis, B is in the XY plane. Ignored if CELL_FILE_NAME is used.

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ALPHA_BETA_GAMMA

Type: real[3]
Default: 9.00000000E+001 9.00000000E+001 9.00000000E+001 [deg]
Aliases: ANGLES
Usage: ALPHA_BETA_GAMMA [deg] 90.0 90.0 120.0

Description: Specify the angles between the vectors A, B and C when using the ABC keyword. The convention is that A lies along the X-axis, B is in the XY plane. ALPHA is the angle between B and C, BETA is the angle between A and C and GAMMA is the angle between A and B.

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B

Type: real[3]
Default: [angstrom]
Usage: B 0.000 10.000 0.000

Description: Specify the Cartesian components for the cell vector B. This defines the second column of the h matrix. Ignored if the keywords ABC or CELL_FILE_NAME are used.

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C

Type: real[3]
Default: [angstrom]
Usage: C 0.000 0.000 10.000

Description: Specify the Cartesian components for the cell vector C. This defines the third column of the h matrix. Ignored if the keywords ABC or CELL_FILE_NAME are used.

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CANONICALIZE

Type: enum
Default: AUTO
Lone keyword: TRUE
Usage: CANONICALIZE AUTO

Description: Policy for transforming a general input cell to CP2K’s internal convention that A lies along the X-axis and B is in the XY plane. AUTO is conservative and keeps the input orientation when a silent transformation could affect Cartesian or direction-dependent input. TRUE explicitly requests canonicalization and transforms supported cell-dependent input. FALSE always keeps the input orientation.

Valid values:

  • AUTO Keep the input orientation unless canonicalization is unambiguously safe

  • TRUE Explicitly canonicalize the input cell

  • FALSE Keep the input cell orientation

  • T Alias for TRUE

  • F Alias for FALSE

  • .TRUE. Alias for TRUE

  • .FALSE. Alias for FALSE

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CELL_FILE_FORMAT

Type: enum
Default: CP2K
Usage: CELL_FILE_FORMAT (CP2K|CIF|XSC|EXTXYZ|XYZ|PDB)

Description: Format of the external file from which cell is parsed. If the format specifies a cell by lengths and angles of three vectors, then a cell matrix is constructed with the convention that A lies along the X-axis, B is in the XY plane. ALPHA is the angle between B and C, BETA is the angle between A and C, and GAMMA is the angle between A and B.

Valid values:

  • CP2K Cell info in the CP2K native format

  • CIF Cell info from CIF file (from fields _cell_length_a or _cell.length_a, etc)

  • XSC Cell info in the XSC format (NAMD)

  • EXTXYZ Cell info as lattice=... field in the comment line of Extended XYZ format

  • XYZ Alias for Extended XYZ

  • PDB Cell info in the CRYST1 record of PDB format

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CELL_FILE_NAME

Type: string
Usage: CELL_FILE_NAME

Description: The external file from which cell is parsed

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MULTIPLE_UNIT_CELL

Type: integer[3]
Default: 1 1 1
Usage: MULTIPLE_UNIT_CELL 1 1 1

Description: Specifies the numbers of repetition in space (X, Y, Z) of the defined cell, assuming it as a unit cell. This keyword affects only the CELL specification. The same keyword in SUBSYS%TOPOLOGY%MULTIPLE_UNIT_CELL should be modified in order to affect the coordinates specification.

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PERIODIC

Type: enum
Default: XYZ
Usage: PERIODIC (x|y|z|xy|xz|yz|xyz|none)

Description: Specify the directions for which periodic boundary conditions (PBC) will be applied. Important notice: This applies to the generation of the pair lists as well as to the application of the PBCs to positions. See the POISSON section to specify the periodicity used for the electrostatics. Typically the settings should be the same.

Valid values:

  • X

  • Y

  • Z

  • XY

  • XZ

  • YZ

  • XYZ

  • NONE

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SYMMETRY

Type: enum
Default: NONE
Usage: SYMMETRY monoclinic

Description: Imposes an initial cell symmetry, according to the convention that A lies along the X-axis, B is in the XY plane. After the input cell information is parsed, the symmetry is enforced by reconstructing the cell matrix from lengths and angles of the cell vectors, taking averages if necessary. This process does not affect input atomic coordinates; in case a space group is to be detected and preserved for an optimization task, atomic coordinates should correspond to cell vectors already obeying the convention mentioned above.

Valid values:

  • NONE No cell symmetry

  • TRICLINIC Triclinic (a ≠ b ≠ c ≠ a, α ≠ β ≠ γ ≠ α ≠ 90°)

  • MONOCLINIC Monoclinic (a ≠ b ≠ c, α = γ = 90°, β ≠ 90°)

  • MONOCLINIC_GAMMA_AB Monoclinic (a = b ≠ c, α = β = 90°, γ ≠ 90°)

  • ORTHORHOMBIC Orthorhombic (a ≠ b ≠ c, α = β = γ = 90°)

  • TETRAGONAL_AB Tetragonal (a = b ≠ c, α = β = γ = 90°)

  • TETRAGONAL_AC Tetragonal (a = c ≠ b, α = β = γ = 90°)

  • TETRAGONAL_BC Tetragonal (a ≠ b = c, α = β = γ = 90°)

  • TETRAGONAL Tetragonal (alias for TETRAGONAL_AB)

  • RHOMBOHEDRAL Rhombohedral (a = b = c, α = β = γ ≠ 90°)

  • HEXAGONAL Hexagonal (alias for HEXAGONAL_GAMMA_60)

  • HEXAGONAL_GAMMA_60 Hexagonal (a = b ≠ c, α = β = 90°, γ = 60°)

  • HEXAGONAL_GAMMA_120 Hexagonal (a = b ≠ c, α = β = 90°, γ = 120°)

  • CUBIC Cubic (a = b = c, α = β = γ = 90°)

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