forked from lijiext/lammps
109 lines
3.7 KiB
HTML
109 lines
3.7 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_style buck command
|
|
</H3>
|
|
<H3>pair_style buck/coul/cut command
|
|
</H3>
|
|
<H3>pair_style buck/coul/long command
|
|
</H3>
|
|
<P><B>Syntax:</B>
|
|
</P>
|
|
<PRE>pair_style style args
|
|
</PRE>
|
|
<UL><LI>style = <I>buck</I> or <I>buck/coul/cut</I> or <I>buck/coul/long</I>
|
|
<LI>args = list of arguments for a particular style
|
|
</UL>
|
|
<PRE> <I>buck</I> args = cutoff
|
|
cutoff = global cutoff for Buckingham interactions (distance units)
|
|
<I>buck/coul/cut</I> args = cutoff (cutoff2)
|
|
cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
|
|
cutoff2 = global cutoff for Coulombic (optional) (distance units)
|
|
<I>buck/coul/long</I> args = cutoff (cutoff2)
|
|
cutoff = global cutoff for Buckingham (and Coulombic if only 1 arg) (distance units)
|
|
cutoff2 = global cutoff for Coulombic (optional) (distance units)
|
|
</PRE>
|
|
<P><B>Examples:</B>
|
|
</P>
|
|
<PRE>pair_style buck 2.5
|
|
pair_coeff * * 100.0 1.5 200.0
|
|
pair_coeff * * 100.0 1.5 200.0 3.0
|
|
</PRE>
|
|
<PRE>pair_style buck/coul/cut 10.0
|
|
pair_style buck/coul/cut 10.0 8.0
|
|
pair_coeff * * 100.0 1.5 200.0
|
|
pair_coeff 1 1 100.0 1.5 200.0 9.0
|
|
pair_coeff 1 1 100.0 1.5 200.0 9.0 8.0
|
|
</PRE>
|
|
<PRE>pair_style buck/coul/long 10.0
|
|
pair_style buck/coul/long 10.0 8.0
|
|
pair_coeff * * 100.0 1.5 200.0
|
|
pair_coeff 1 1 100.0 1.5 200.0 9.0
|
|
</PRE>
|
|
<P><B>Description:</B>
|
|
</P>
|
|
<P>The <I>buck</I> style computes a Buckingham potential (exp/6 instead of
|
|
Lennard-Jones 12/6) given by
|
|
</P>
|
|
<CENTER><IMG SRC = "Eqs/pair_buck.jpg">
|
|
</CENTER>
|
|
<P>Rc is the cutoff.
|
|
</P>
|
|
<P>The <I>buck/coul/cut</I> and <I>buck/coul/long</I> styles add a Coulombic term
|
|
as described for the <A HREF = "pair_style_lj.html">lj/cut</A> pair styles.
|
|
</P>
|
|
<P>The following coefficients must be defined for each pair of atoms
|
|
types via the <A HREF = "pair_coeff.html">pair_coeff</A> command as in the examples
|
|
above, or in the data file or restart files read by the
|
|
<A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
|
|
commands:
|
|
</P>
|
|
<UL><LI>A (energy units)
|
|
<LI>rho (distance units)
|
|
<LI>C (energy-distance^6 units)
|
|
<LI>cutoff (distance units)
|
|
<LI>cutoff2 (distance units)
|
|
</UL>
|
|
<P>The latter 2 coefficients are optional. If not specified, the global
|
|
LJ and Coulombic cutoffs are used. If only one cutoff is specified,
|
|
it is used as the cutoff for both LJ and Coulombic interactions for
|
|
this type pair. If both coefficients are specified, they are used as
|
|
the LJ and Coulombic cutoffs for this type pair. You cannot specify 2
|
|
cutoffs for style <I>buck</I>, since it has no Coulombic terms.
|
|
</P>
|
|
<P>For <I>buck/coul/long</I> only the LJ cutoff can be specified since a
|
|
Coulombic cutoff cannot be specified for an individual I,J type pair.
|
|
All type pairs use the same global Coulombic cutoff specified in the
|
|
pair_style command.
|
|
</P>
|
|
<P><B>Restrictions:</B>
|
|
</P>
|
|
<P>The <I>buck</I> potentials do not support the
|
|
<A HREF = "pair_modify.hmtl">pair_modify</A> <I>mix</I> option. Coefficients for all i,j
|
|
pairs must be specified explicitly.
|
|
</P>
|
|
<P>The <I>buck/coul/long</I> style is part of the "kspace" package. It is
|
|
only enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_2">Making
|
|
LAMMPS</A> section for more info.
|
|
</P>
|
|
<P>On some 64-bit machines, compiling with -O3 appears to break the
|
|
Coulombic tabling option used by the <I>buck/coul/long</I> style. See
|
|
the "Additional build tips" section of the Making LAMMPS documentation
|
|
pages for workarounds on this issue.
|
|
</P>
|
|
<P><B>Related commands:</B>
|
|
</P>
|
|
<P><A HREF = "pair_coeff.html">pair_coeff</A>
|
|
</P>
|
|
<P><B>Default:</B> none
|
|
</P>
|
|
</HTML>
|