2007-06-11 23:48:57 +08:00
|
|
|
<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>shape command
|
|
|
|
|
</H3>
|
|
|
|
|
<P><B>Syntax:</B>
|
|
|
|
|
</P>
|
2008-06-07 01:07:59 +08:00
|
|
|
<PRE>shape I x y z
|
2007-06-11 23:48:57 +08:00
|
|
|
</PRE>
|
2008-03-01 09:13:20 +08:00
|
|
|
<UL><LI>I = atom type (see asterisk form below)
|
2009-01-20 01:17:01 +08:00
|
|
|
<LI>x = x diameter (distance units)
|
|
|
|
|
<LI>y = y diameter (distance units)
|
|
|
|
|
<LI>z = z diameter (distance units)
|
2007-06-11 23:48:57 +08:00
|
|
|
</UL>
|
|
|
|
|
<P><B>Examples:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<PRE>shape 1 1.0 1.0 1.0
|
|
|
|
|
shape * 3.0 1.0 1.0
|
|
|
|
|
shape 2* 3.0 1.0 1.0
|
|
|
|
|
</PRE>
|
|
|
|
|
<P><B>Description:</B>
|
|
|
|
|
</P>
|
2009-01-20 01:17:01 +08:00
|
|
|
<P>Set the shape for all atoms of one or more atom types. In LAMMPS,
|
|
|
|
|
particles that have a finite size are said to have a "shape", as
|
2009-06-27 02:22:33 +08:00
|
|
|
opposed to being a point mass. The shape can be spherical or
|
|
|
|
|
aspherical, depending on whether the 3 shape values are the same or
|
|
|
|
|
different. Shape values can also be set in the
|
2009-01-20 01:17:01 +08:00
|
|
|
<A HREF = "read_data.html">read_data</A> data file using the "Shapes" keyword. See
|
|
|
|
|
the <A HREF = "units.html">units</A> command for what distance units to use.
|
2007-06-11 23:48:57 +08:00
|
|
|
</P>
|
2007-06-20 20:56:25 +08:00
|
|
|
<P>The I index can be specified in one of two ways. An explicit numeric
|
|
|
|
|
value can be used, as in the 1st example above. Or a wild-card
|
2008-06-07 01:07:59 +08:00
|
|
|
asterisk can be used to set the shape for multiple atom types. This
|
2007-06-20 20:56:25 +08:00
|
|
|
takes the form "*" or "*n" or "n*" or "m*n". If N = the number of
|
2008-03-01 09:13:20 +08:00
|
|
|
atom types, then an asterisk with no numeric values means all types
|
|
|
|
|
from 1 to N. A leading asterisk means all types from 1 to n
|
|
|
|
|
(inclusive). A trailing asterisk means all types from n to N
|
|
|
|
|
(inclusive). A middle asterisk means all types from m to n
|
2007-06-20 20:56:25 +08:00
|
|
|
(inclusive).
|
2007-06-11 23:48:57 +08:00
|
|
|
</P>
|
2009-01-20 01:17:01 +08:00
|
|
|
<P>A line in a <A HREF = "read_data.html">data file</A> that follows the "Shapes"
|
|
|
|
|
keyword specifies shape using the same format as the arguments of the
|
|
|
|
|
shape command in an input script, except that no wild-card asterisk
|
|
|
|
|
can be used. For example, under the "Shapes" section of a data file,
|
|
|
|
|
the line that corresponds to the 1st example above would be listed as
|
2007-06-11 23:48:57 +08:00
|
|
|
</P>
|
2007-06-20 20:56:25 +08:00
|
|
|
<PRE>1 1.0 1.0 1.0
|
2007-06-11 23:48:57 +08:00
|
|
|
</PRE>
|
2009-06-27 02:22:33 +08:00
|
|
|
<P>The shape values can be set to all 0.0, which means that atoms of that
|
|
|
|
|
type are point particles and not finite-size particles. Some pair
|
|
|
|
|
styles and fixes and computes that operate on finite-size particles
|
|
|
|
|
allow for a mixture of finite-size and point particles. See the doc
|
|
|
|
|
pages of individual commands for details.
|
2009-01-20 01:17:01 +08:00
|
|
|
</P>
|
|
|
|
|
<P>Note that the shape command can only be used if the <A HREF = "atom_style.html">atom
|
|
|
|
|
style</A> requires per-type atom shape to be set.
|
|
|
|
|
Currently, only the <I>dipole</I> and <I>ellipsoid</I> styles do. The
|
|
|
|
|
<I>granular</I> and <I>peri</I> styles require the shape to be set for indivual
|
|
|
|
|
particles, not types. For these styles, the only option currently
|
|
|
|
|
allowed is for spherical particles, so a single diameter value
|
|
|
|
|
suffices to determine the shape. Per-atom diameters are defined in
|
|
|
|
|
the data file read by the <A HREF = "read_data.html">read_data</A> command, or set
|
|
|
|
|
to default values by the <A HREF = "create_atoms.html">create_atoms</A> command, or
|
|
|
|
|
set to new values by the <A HREF = "set.html">set diamter</A> command.
|
|
|
|
|
</P>
|
|
|
|
|
<P>Dipoles use the atom shape to compute a moment of inertia for
|
|
|
|
|
rotational energy. See the <A HREF = "pair_dipole.html">pair_style dipole</A>
|
|
|
|
|
command. Only the 1st component of the shape is used since the
|
|
|
|
|
particles are assumed to be spherical.
|
|
|
|
|
</P>
|
|
|
|
|
<P>Ellipsoids use the atom shape to compute a generalized inertia tensor.
|
|
|
|
|
For example, a shape setting of 3.0 1.0 1.0 defines a particle 3x
|
|
|
|
|
longer in x than in y or z and with a circular cross-section in yz.
|
|
|
|
|
Degenerate ellipsoids which are spherical can be defined by setting
|
|
|
|
|
all 3 shape components the same.
|
|
|
|
|
</P>
|
|
|
|
|
<P>If you define a <A HREF = "atom_style.html">hybrid atom style</A> which includes one
|
|
|
|
|
(or more) sub-styles which require per-type shape and one (or more)
|
2009-06-27 02:22:33 +08:00
|
|
|
sub-styles which require per-atom diameter, then you must define both.
|
|
|
|
|
In this case the per-type shape will be ignored; only the per-atom
|
|
|
|
|
diameter will be used by LAMMPS. Note that this means you can not
|
|
|
|
|
currently mix aspherical particles with per-atom diameter particles.
|
2009-01-20 01:17:01 +08:00
|
|
|
</P>
|
2007-06-11 23:48:57 +08:00
|
|
|
<P><B>Restrictions:</B>
|
|
|
|
|
</P>
|
|
|
|
|
<P>This command must come after the simulation box is defined by a
|
|
|
|
|
<A HREF = "read_data.html">read_data</A>, <A HREF = "read_restart.html">read_restart</A>, or
|
|
|
|
|
<A HREF = "create_box.html">create_box</A> command.
|
|
|
|
|
</P>
|
|
|
|
|
<P>All shapes must be defined before a simulation is run (if the atom
|
|
|
|
|
style requires shapes be set).
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Related commands:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
<P><B>Default:</B> none
|
|
|
|
|
</P>
|
|
|
|
|
</HTML>
|
