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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@2620 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2009-03-04 17:24:41 +00:00
parent 7b88b08c3a
commit 6799a16b3b
2 changed files with 32 additions and 20 deletions
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26
doc/fix_rigid.html
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@ -56,11 +56,13 @@ means that each timestep the total force and torque on each rigid body
is computed and the coordinates and velocities of the atoms in each
body are updated so that they move as a rigid body. This can be
useful for freezing one or more portions of a large biomolecule, or
for simulating a system of colloidal particles.
for simulating a system of colloidal particles. See the Restrictions
section if you simply want to hold a group of atoms motionless or have
them move with constant velocity.
</P>
<P>This fix updates the positions and velocities of the rigid atoms with
a constant-energy time integration, so you should not update the same
atoms via other fixes (e.g. nve, nvt, npt).
<P>IMPORTANT NOTE: This fix updates the positions and velocities of the
rigid atoms with a constant-energy time integration, so you should not
update the same atoms via other fixes (e.g. nve, nvt, npt).
</P>
<P>Each body must have two or more atoms. An atom can belong to at most
one rigid body. Which atoms are in which bodies can be defined via
@ -193,12 +195,16 @@ boundary, the input data file must define the image flags for each
atom correctly, so that LAMMPS can "unwrap" the atoms into a valid
rigid body.
</P>
<P>You should not use this fix if you just want to hold group of atoms
stationary. A better way to do this is to not include those atoms in
your time integration fix. E.g. use "fix 1 mobile nve" instead of
"fix 1 all nve", where "mobile" is the group of atoms that you want to
move. Alternatively, you can also set the force on those atoms to 0.0
via the <A HREF = "fix_setforce.html">fix setforce</A> command.
<P>This fix is overkill if you just want to hold group of atoms
stationary of have them move with a constant velocity. A simpler way
to hold atoms stationary is to not include those atoms in your time
integration fix. E.g. use "fix 1 mobile nve" instead of "fix 1 all
nve", where "mobile" is the group of atoms that you want to move. You
can move atoms with a constant velocity by assigning them an initial
velocity (via the <A HREF = "velocity.html">velocity</A> command), setting the force
on them to 0.0 (via the <A HREF = "fix_setforce.html">fix setforce</A> command), and
integrating them as usual (e.g. via the <A HREF = "fix_nve.html">fix nve</A>
command).
</P>
<P><B>Related commands:</B>
</P>

26
doc/fix_rigid.txt
View File

@ -47,11 +47,13 @@ means that each timestep the total force and torque on each rigid body
is computed and the coordinates and velocities of the atoms in each
body are updated so that they move as a rigid body. This can be
useful for freezing one or more portions of a large biomolecule, or
for simulating a system of colloidal particles.
for simulating a system of colloidal particles. See the Restrictions
section if you simply want to hold a group of atoms motionless or have
them move with constant velocity.
This fix updates the positions and velocities of the rigid atoms with
a constant-energy time integration, so you should not update the same
atoms via other fixes (e.g. nve, nvt, npt).
IMPORTANT NOTE: This fix updates the positions and velocities of the
rigid atoms with a constant-energy time integration, so you should not
update the same atoms via other fixes (e.g. nve, nvt, npt).
Each body must have two or more atoms. An atom can belong to at most
one rigid body. Which atoms are in which bodies can be defined via
@ -184,12 +186,16 @@ boundary, the input data file must define the image flags for each
atom correctly, so that LAMMPS can "unwrap" the atoms into a valid
rigid body.
You should not use this fix if you just want to hold group of atoms
stationary. A better way to do this is to not include those atoms in
your time integration fix. E.g. use "fix 1 mobile nve" instead of
"fix 1 all nve", where "mobile" is the group of atoms that you want to
move. Alternatively, you can also set the force on those atoms to 0.0
via the "fix setforce"_fix_setforce.html command.
This fix is overkill if you just want to hold group of atoms
stationary of have them move with a constant velocity. A simpler way
to hold atoms stationary is to not include those atoms in your time
integration fix. E.g. use "fix 1 mobile nve" instead of "fix 1 all
nve", where "mobile" is the group of atoms that you want to move. You
can move atoms with a constant velocity by assigning them an initial
velocity (via the "velocity"_velocity.html command), setting the force
on them to 0.0 (via the "fix setforce"_fix_setforce.html command), and
integrating them as usual (e.g. via the "fix nve"_fix_nve.html
command).
[Related commands:]