forked from lijiext/lammps
85 lines
2.9 KiB
Plaintext
85 lines
2.9 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
|
|
|
:link(lws,http://lammps.sandia.gov)
|
|
:link(ld,Manual.html)
|
|
:link(lc,Section_commands.html#comm)
|
|
|
|
:line
|
|
|
|
fix smd/setvel command :h3
|
|
|
|
[Syntax:]
|
|
|
|
fix ID group-ID smd/setvel vx vy vz keyword value ... :pre
|
|
|
|
ID, group-ID are documented in "fix"_fix.html command :ulb,l
|
|
smd/setvel = style name of this fix command :l
|
|
vx,vy,vz = velocity component values :l
|
|
any of vx,vy,vz can be a variable (see below) :l
|
|
zero or more keyword/value pairs may be appended to args :l
|
|
keyword = {region} :l
|
|
{region} value = region-ID
|
|
region-ID = ID of region particles must be in to have their velocities set :pre
|
|
:ule
|
|
|
|
[Examples:]
|
|
|
|
fix top_velocity top_group setvel 1.0 0.0 0.0 :pre
|
|
|
|
[Description:]
|
|
|
|
Set each component of velocity on each particle in the group to the specified
|
|
values vx,vy,vz, regardless of the forces acting on the particle. This command can
|
|
be used to impose velocity boundary conditions.
|
|
|
|
Any of the vx,vy,vz values can be specified as NULL which means do not
|
|
alter the velocity component in that dimension.
|
|
|
|
This fix is indented to be used together with a time integration fix.
|
|
|
|
Any of the 3 quantities defining the velocity components can be specified
|
|
as an equal-style or atom-style "variable"_variable.html, namely {vx},
|
|
{vy}, {vz}. If the value is a variable, it should be specified as
|
|
v_name, where name is the variable name. In this case, the variable
|
|
will be evaluated each timestep, and its value used to determine the
|
|
force component.
|
|
|
|
Equal-style variables can specify formulas with various mathematical
|
|
functions, and include "thermo_style"_thermo_style.html command
|
|
keywords for the simulation box parameters and timestep and elapsed
|
|
time. Thus it is easy to specify a time-dependent velocity field.
|
|
|
|
Atom-style variables can specify the same formulas as equal-style
|
|
variables but can also include per-atom values, such as atom
|
|
coordinates. Thus it is easy to specify a spatially-dependent velocity
|
|
field with optional time-dependence as well.
|
|
|
|
If the {region} keyword is used, the particle must also be in the
|
|
specified geometric "region"_region.html in order to have its velocity set by this command.
|
|
|
|
:line
|
|
|
|
[Restart, fix_modify, output, run start/stop, minimize info:]
|
|
|
|
Currently, no part of USER-SMD supports restarting nor minimization
|
|
None of the "fix_modify"_fix_modify.html options
|
|
are relevant to this fix.
|
|
|
|
This fix computes a global 3-vector of forces, which can be accessed
|
|
by various "output commands"_Section_howto.html#howto_15. This is the
|
|
total force on the group of atoms. The vector values calculated by this
|
|
fix are "extensive".
|
|
|
|
No parameter of this fix can be used with the {start/stop} keywords of
|
|
the "run"_run.html command.
|
|
|
|
[Restrictions:]
|
|
|
|
This fix is part of the USER-SMD package. It is only enabled if
|
|
LAMMPS was built with that package. See the "Making LAMMPS"_Section_start.html#start_3
|
|
section for more info.
|
|
|
|
[Related commands:] none
|
|
|
|
[Default:] none
|