forked from lijiext/lammps
88 lines
3.1 KiB
HTML
88 lines
3.1 KiB
HTML
<HTML>
|
|
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
|
|
</CENTER>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<HR>
|
|
|
|
<H3>displace_atoms command
|
|
</H3>
|
|
<P><B>Syntax:</B>
|
|
</P>
|
|
<PRE>displace_atoms group-ID style args keyword value ...
|
|
</PRE>
|
|
<UL><LI>group-ID = ID of group of atoms to displace
|
|
|
|
<LI>style = <I>move</I> or <I>ramp</I>
|
|
|
|
<PRE> <I>move</I> args = delx dely delz
|
|
delx,dely,delz = distance to displace in each dimension (distance units)
|
|
<I>ramp</I> args = ddim dlo dhi dim clo chi
|
|
ddim = <I>x</I> or <I>y</I> or <I>z</I>
|
|
dlo,dhi = displacement distance between dlo and dhi (distance units)
|
|
dim = <I>x</I> or <I>y</I> or <I>z</I>
|
|
clo,chi = lower and upper bound of domain to displace (distance units)
|
|
</PRE>
|
|
<LI>zero or more keyword/value pairs may be appended to the args
|
|
|
|
<PRE> keyword = <I>units</I>
|
|
value = <I>box</I> or <I>lattice</I>
|
|
</PRE>
|
|
|
|
</UL>
|
|
<P><B>Examples:</B>
|
|
</P>
|
|
<PRE>displace_atoms top move 0 -5 0 units box
|
|
displace_atoms flow ramp x 0.0 5.0 y 2.0 20.5
|
|
</PRE>
|
|
<P><B>Description:</B>
|
|
</P>
|
|
<P>Displace a group of atoms. This can be used to move atoms a large
|
|
distance before beginning a simulation. For example, in a shear
|
|
simulation, an initial strain can be imposed on the system. Or two
|
|
groups of atoms can be brought into closer proximity.
|
|
</P>
|
|
<P>The <I>move</I> style displaces the group of atoms by the specified 3d
|
|
distance. The <I>ramp</I> style displaces atoms a variable amount in one
|
|
dimension depending on the atom's coordinate in a (possibly) different
|
|
dimension. For example, the second example command displaces atoms in
|
|
the x-direction an amount between 0.0 and 5.0 distance units. Each
|
|
atom's displacement depends on the fractional distance its y
|
|
coordinate is between 2.0 and 20.5. Atoms with y-coordinates outside
|
|
those bounds will be moved the minimum (0.0) or maximum (5.0) amount.
|
|
</P>
|
|
<P>Distance units for the displacement are determined by the setting of
|
|
<I>box</I> or <I>lattice</I> for the <I>units</I> keyword. <I>Box</I> means distance
|
|
units as defined by the <A HREF = "units.html">units</A> command - e.g. Angstroms
|
|
for <I>real</I> units. <I>Lattice</I> means distance units are in lattice
|
|
spacings. The <A HREF = "lattice.html">lattice</A> command must have been
|
|
previously used to define the lattice spacing.
|
|
</P>
|
|
<P>Care should be taken not to move atoms on top of other atoms. After
|
|
the move, atoms are remapped to the periodic simulation box. In
|
|
parallel, atoms should not be moved so far that they cross more than
|
|
one processor's sub-domain, else they may be lost. If this is a
|
|
problem, successive displace_atom commands can be used to move atoms a
|
|
large distance.
|
|
</P>
|
|
<P><B>Restrictions:</B>
|
|
</P>
|
|
<P>This command requires inter-processor communication to migrate atoms
|
|
once they have been displaced. This means that your system must be
|
|
ready to perform a simulation before using this command (force fields
|
|
are setup, atom masses are set, etc).
|
|
</P>
|
|
<P><B>Related commands:</B>
|
|
</P>
|
|
<P><A HREF = "lattice.html">lattice</A>
|
|
</P>
|
|
<P><B>Default:</B>
|
|
</P>
|
|
<P>The option defaults are units = lattice.
|
|
</P>
|
|
</HTML>
|