forked from lijiext/lammps
70 lines
2.3 KiB
Plaintext
70 lines
2.3 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 addforce command :h3
|
|
|
|
[Syntax:]
|
|
|
|
fix ID group-ID addforce fx fy fz :pre
|
|
|
|
ID, group-ID are documented in "fix"_fix.html command
|
|
addforce = style name of this fix command
|
|
fx,fy,fz = force component values (force units) :ul
|
|
|
|
[Examples:]
|
|
|
|
fix kick flow addforce 1.0 0.0 0.0 :pre
|
|
|
|
[Description:]
|
|
|
|
Add fx,fy,fz to the corresponding component of force for each atom in
|
|
the group. This command can be used to give an additional push to
|
|
atoms in a simulation, such as for a simulation of Poiseuille flow in
|
|
a channel.
|
|
|
|
[Restart, fix_modify, output, run start/stop, minimize info:]
|
|
|
|
No information about this fix is written to "binary restart
|
|
files"_restart.html.
|
|
|
|
The "fix_modify"_fix_modify.html {energy} option is supported by this
|
|
fix to add the potential "energy" inferred by the added force to the
|
|
system's potential energy as part of "thermodynamic
|
|
output"_thermo_style.html. This is a fictitious quantity but is
|
|
needed so that the "minimize"_minimize.html command can include the
|
|
forces added by this fix in a consistent manner. I.e. there is a
|
|
decrease in potential energy when atoms move in the direction of the
|
|
added force.
|
|
|
|
This fix computes a scalar and a 3-vector of forces, which can be
|
|
accessed by various "output commands"_Section_howto.html#4_15. The
|
|
scalar is the potential energy discussed above. The vector is the
|
|
total force on the group of atoms before the forces on individual
|
|
atoms are changed by the fix. The scalar vector values calculated by
|
|
this fix are "extensive", meaning they scale with the number of atoms
|
|
in the simulation.
|
|
|
|
No parameter of this fix can be used with the {start/stop} keywords of
|
|
the "run"_run.html command.
|
|
|
|
The forces due to this fix are imposed during an energy minimization,
|
|
invoked by the "minimize"_minimize.html command.
|
|
|
|
IMPORTANT NOTE: If you want the fictitious potential energy associated
|
|
with the added forces to be included in the total potential energy of
|
|
the system (the quantity being minimized), you MUST enable the
|
|
"fix_modify"_fix_modify.html {energy} option for this fix.
|
|
|
|
[Restrictions:] none
|
|
|
|
[Related commands:]
|
|
|
|
"fix setforce"_fix_setforce.html, "fix aveforce"_fix_aveforce.html
|
|
|
|
[Default:] none
|