fix particletemplate/fragments command

Syntax

fix ID group-ID particletemplate/fragments seed keyword values ...

  • ID, group-ID are documented in fix command

  • particletemplate/fragments = style name of this fix command

  • seed = random number generator seed (integer value)

  • zero or more keyword/value pairs can be appended

  • keyword = atom_type or density or breakage_index or tn_family or maxattempt or omit_radius

    atom_type value = atom type assigned to this particle template
density values = random_style param1 (param2)
  random_style = 'constant' or 'uniform' or 'gaussian'
  param1 = density for 'constant', low value of density for 'uniform', expectancy value for 'gaussian'
  param2 = omitted for 'constant', high value of density for 'uniform', sigma value for 'gaussian'
breakage_index values = A minsize
  A = maximum achievable t10 in a single breakage event
  minsize = minimum size of generated fragments (fraction of parent particle size)
tn_family values = n frac1 (frac2 ...)
  n = number of size distribution curves tn to use
  frac = tn family curve to use
maxattempt value = n
  n = number of attempts to pack a fragment into the volume of the parent particle with minimum overlap
omit_radius values = ogenerate orad
  ogenerate = omit fragments pre or post generation of actual size distribution
  orad = minimum radius below which fragments will be removed from simulation

Examples

fix pts3 all particletemplate/fragments 321 atom_type 1 density constant 2500 breakage_index 0.1 0.095 tn_family 3 2 5 10

LIGGGHTS vs. LAMMPS Info:

This LIGGGHTS command is not available in LAMMPS.

Description

Define a particle template that is used as input for a fix_particledistribution_discrete command to produce fragments of particles for the discrete fragmentation method (DFM).

You can choose the atom type, density and radius distribution of the particles. For density, you can choose between ‘constant’, ‘uniform’ and ‘gaussian’ random styles. The radius distribution is determined by the breakage index t10 calculated from the breakage probability P of a fix_break_particle

images/fix_particletemplate_fragments.png

t10 is the cumulative mass percentage of the fragments which are smaller than 1/10 of the parent particle size and A is the maximum achievable t10 in a single breakage event. This parameter is uniquely related to other points on a family of size distribution curves tn, thus yielding the particle size distribution (PSD).

The breakage_index option defines A and the minimum size of fragments created (specified as fraction of the parent particle size).

The tn_family values specify the tn family curves used to generate the size distribution of fragments.

The maxattempt option determines the number of attempts to pack a fragment into the volume of the parent particle with a minimum overlap. Note that if this value is exceeded, large overlaps of fragments may occur.

The omit_radius option allows to neglect fragments below a certain size to speed up the simulation. This can be done by either subtracting the corresponding mass fraction from the parent particle mass (keyword pre) or by generating the size distribution from the given tn family curves and subsequently omitting fragments which are smaller than the given radius (keyword post).

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

Information about the random state in this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global scalar or vector or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions

none