forked from lijiext/lammps
81 lines
3.0 KiB
HTML
81 lines
3.0 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>pair_write command
|
||
|
|
</H3>
|
||
|
|
<P><B>Syntax:</B>
|
||
|
|
</P>
|
||
|
|
<PRE>pair_write itype jtype N style inner outer file keyword Qi Qj
|
||
|
|
</PRE>
|
||
|
|
<UL><LI>itype,jtype = 2 atom types
|
||
|
|
<LI>N = # of values
|
||
|
|
<LI>style = <I>r</I> or <I>rsq</I> or <I>bitmap</I>
|
||
|
|
<LI>inner,outer = inner and outer cutoff (distance units)
|
||
|
|
<LI>file = name of file to write values to
|
||
|
|
<LI>keyword = section name in file for this set of tabulated values
|
||
|
|
<LI>Qi,Qj = 2 atom charges (charge units) (optional)
|
||
|
|
</UL>
|
||
|
|
<P><B>Examples:</B>
|
||
|
|
</P>
|
||
|
|
<PRE>pair_write 1 3 500 r 1.0 10.0 table.txt LJ
|
||
|
|
pair_write 1 1 1000 rsq 2.0 8.0 table.txt Yukawa_1_1 -0.5 0.5
|
||
|
|
</PRE>
|
||
|
|
<P><B>Description:</B>
|
||
|
|
</P>
|
||
|
|
<P>Write energy and force values to a file as a function of distance for
|
||
|
|
the currently defined pair potential. This is useful for plotting the
|
||
|
|
potential function or otherwise debugging its values. If the file
|
||
|
|
already exists, the table of values is appended to the end of the file
|
||
|
|
to allow multiple tables of energy and force to be included in one
|
||
|
|
file.
|
||
|
|
</P>
|
||
|
|
<P>The energy and force values are computed at distances from inner to
|
||
|
|
outer for 2 interacting atoms of type itype and jtype, using the
|
||
|
|
appropriate <A HREF = "pair_coeff.html">pair_coeff</A> coefficients. If the style
|
||
|
|
is <I>r</I>, then N distances are used, evenly spaced in r; if the style is
|
||
|
|
<I>rsq</I>, N distances are used, evenly spaced in r^2.
|
||
|
|
</P>
|
||
|
|
<P>For example, for N = 7, style = <I>r</I>, inner = 1.0, and outer = 4.0,
|
||
|
|
values are computed at r = 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0.
|
||
|
|
</P>
|
||
|
|
<P>If the style is <I>bitmap</I>, then 2^N values are written to the file in a
|
||
|
|
format and order consistent with how they are read in by the
|
||
|
|
<A HREF = "pair_coeff.html">pair_coeff</A> command for pair style <I>table</I>. For
|
||
|
|
reasonable accuracy in a bitmapped table, choose N >= 12, an <I>inner</I>
|
||
|
|
value that is smaller than the distance of closest approach of 2
|
||
|
|
atoms, and an <I>outer</I> value <= cutoff of the potential.
|
||
|
|
</P>
|
||
|
|
<P>If the pair potential is computed between charged atoms, the charges
|
||
|
|
of the pair of interacting atoms can optionally be specified. If not
|
||
|
|
specified, values of Qi = Qj = 1.0 are used.
|
||
|
|
</P>
|
||
|
|
<P>The file is written in the format used as input for the
|
||
|
|
<A HREF = "pair_style.html">pair_style</A> <I>table</I> option with <I>keyword</I> as the
|
||
|
|
section name. Each line written to the file lists an index number
|
||
|
|
(1-N), a distance (in distance units), an energy (in energy units),
|
||
|
|
and a force (in force units).
|
||
|
|
</P>
|
||
|
|
<P><B>Restrictions:</B>
|
||
|
|
</P>
|
||
|
|
<P>All force field coefficients for pair and other kinds of interactions
|
||
|
|
must be set before this command can be invoked.
|
||
|
|
</P>
|
||
|
|
<P>Due to how the pairwise force is computed, an inner value > 0.0 must
|
||
|
|
be specified even if the potential has a finite value at r = 0.0.
|
||
|
|
</P>
|
||
|
|
<P><B>Related commands:</B>
|
||
|
|
</P>
|
||
|
|
<P><A HREF = "pair_style.html">pair_style</A>, <A HREF = "pair_coeff.html">pair_coeff</A>
|
||
|
|
</P>
|
||
|
|
<P><B>Default:</B> none
|
||
|
|
</P>
|
||
|
|
</HTML>
|