LIGGGHTS WWW Site - LIGGGHTS Documentation - LIGGGHTS Commands
Syntax:
fix ID group-ID pour/dev target_speficier target seed keyword values ...
ID, group-ID are documented in fix command
pour/dev/packing = style name of this fix command
seed = random # seed (positive integer)
one or more keyword/value pairs may be appended to args
keyword = distributiontemplate and region or vol or vel or regionexempts
distributiontemplate value = dist-fix-ID dist-fix-ID = ID of fix of type particledistribution/discrete to be used region value = region-ID region-ID = ID of region to use as insertion volume regionexempts values = n_exempts region-ID_1 region-ID_2 ... n_exempts = number of regions to exempt from insertion volume region-ID_i = ID of region # i to exempt from insertion volume vol values = fraction Nattempt fraction = desired volume fraction for filling insertion volume Nattempt = max # of insertion attempts per atom vel values (3d) = random_style vx_param1 vx_param2 vy_param1 vy_param2 vz vel values (2d) = random_style vx_param1 vx_param2 vy for style 'uniform': vx_param1/vy_param1,vx_param2/vy_param2 = lo,hi values for range of x velocities/y velocities for inserted particles (distance units) for style 'gaussian': param1,param2 = mu,sigma values for range of x velocities/y velocities for inserted particles (distance units) vz = z velocity (3d) assigned to inserted particles (velocity units) vy = y velocity (2d) assigned to inserted particles (velocity units)
Examples:
fix ins all pour/dev/packing 1 distributiontemplate pdd1 vol 0.2 30 region reg
LIGGGHTS vs. LAMMPS Info:
This LIGGGHTS command fis not available in LAMMPS.
Description:
Insert particles into a granular run once within a specified region. This is useful for particle packing applications.
This command must use the distributiontemplate keyword to refer to a fix of type particledistribution/discrete (defined by dist-fix-ID) that defines the properties of the particles to be inserted r the insertion.
Inserted particles are assigned the properties as defined by the fix particledistribution/discrete and are assigned to two groups: the default group "all" and the group specified in the fix pour command (which can also be "all").
This command must use the region keyword to define an insertion volume. The specified region must have been previously defined with a region command. It must be of type block or a z-axis cylinder and must be defined with side = in. The cylinder style of region can only be used with 3d simulations. With the optional regionexempts keyword, you can specify regions to exempt from the insertion region. These regions can be of any style (see region command). Please note that the target volume fraction is still calculated using the whole insertion volume as specified by the region keyword.
Particles are placed randomly inside the insertion volume. Insertions continue until the desired volume fraction or the specified number of insertion tries have been reached.
All other keywords are optional with defaults as shown below. The vel option enables inserted particles to have a range of xy velocities. The specific values for a particular inserted particle will be chosen randomly where you can choose between uniform and gaussian random styles for vx, vy (for 3d). The vz or vy value for option vel assigns a z-velocity (3d) or y-velocity (2d) to each inserted particle.
The vol option specifies what volume fraction of the insertion volume will be filled with particles. Since inserted particles cannot overlap, the maximum volume fraction should be no higher than about 0.6 (for mono-disperese simulation). Each timestep particles are inserted, LAMMPS will make up to a total of M tries to insert the new particles without overlaps, where M = # of inserted particles * Nattempt. If LAMMPS is unsuccessful at completing all insertions, it prints a warning.
IMPORTANT NOTE: Be careful not to choose the insertion volume too small. Compared to the LAMMPS style fix pour command, the volume has to be larger because the particles are completely located within the insertion volume.
Restart, fix_modify, output, run start/stop, minimize info:
Information about this fix is written to binary restart files . This means you can restart a pouring simulation, when the restart file was written in the middle of the pouring operation.
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:
The specified insertion region cannot be a "dynamic" region, as defined by the region command.
Related commands:
fix_deposit, region , fix_particletemplate_sphere fix_particledistribution_discrete
Default:
The option defaults are vol = 0.25 50, vel = 0.0 0.0 0.0 0.0 0.0.