fix property/global command — LIGGGHTS v3.X documentation

# fix property/global command

# fix property/atom command

## Syntax

    fix id group property/atom variablename style restartvalue comm_ghost_value comm_reverse_ghost_value defaultvalue(s)...
    fix id group property/global variablename style stylearg defaultvalue(s)...

- ID, group-ID are documented in fix command
- property/global or property/atom = style name of this fix command
- variablename = a valid C++ string
- restartvalues = ‘yes’ or ‘no’
- comm_ghost_value = ‘yes’ or ‘no’
- comm_reverse_ghost_value = ‘yes’ or ‘no’

fix property/global:

- style = scalar or vector or atomtype or matrix or atomtypepair

    stylearg for scalar/vector: none
    stylearg for matrix/atomtypepair: nCols

fix property/atom:

- style = scalar or vector
- restartvalue = yes or no
- communicate_ghost_value = yes or no
- communicate_reverse_ghost_value = yes or no

## Examples

    fix m3 all property/global coefficientRestitution peratomtypepair 1 0.3
    fix m5 all property/global characteristicVelocity scalar 2.
    fix uf all property/atom uf vector yes no no  0. 0. 0.

## Description

Fix property/atom reserves per-atom properties to be accessed by the user or other fixes. Style scalar reserves one value per atom, style vector multiple values per atoms, where the number of defaultvalues (that are assigned to the atoms at creation) determines the length of the vector. The group of atoms the fix is applied to is always “all”, irrespective of which group is used for the fix command . If you want to assign different values for different groups, you can use the set command with keyword ‘property/atom’. Keyword restartvalues determines whether information about the values stored by this fix is written to binary restart files. Keyword communicate_ghost_value determines whether information about the values stored by this fix can be communicated to ghost particles (forward communication). The exact location during a time-step when this happens depends on the model that uses this fix. Keyword communicate_reverse_ghost_value determines whether information about the values stored by this fix can be communicated from ghost particles to owned particles (reverse communication). The exact location during a time-step when this happens depends on the model that uses this fix.

Fix property/global reserves global properties to be accessed by the user or other fixes or pair styles. The number of defaultvalues determines the length of the vector / the number of matrix components . For style vector or atomtype, the user provides the number of vector components . For style matrix or atomtypepair, the user provides the number of matrix columns (nCols) .

Example: nCols*= 2 and *defaultvalues = 1 2 3 4 5 6 would be mapped into a matrix like

[ 1 2 ]

[ 3 4 ]

[ 5 6 ]

Note that the number of default values must thus be a multiple of nCols. Note that vector and atomtype do the same thing, atomtype is just provided to make input scripts more readable . Note that matrix and atomtypepair both refer to a matrix of global values. However, a matrix defined via atomtypepair is required to be symmetric.

Note that the group of atoms the fix is applied to is ignored (as the fix is not applied to atoms, but defines values of global scope).

## Restart, fix_modify, output, run start/stop, minimize info

Information about this fix is written to binary restart files if you set restartvalue to ‘yes’.

## Restrictions

> none

## Related commands

set, pair_gran

Default: none