From ab104f0eef45ee0e78bc71d9b3b755906f373587 Mon Sep 17 00:00:00 2001 From: sjplimp <sjplimp@f3b2605a-c512-4ea7-a41b-209d697bcdaa> Date: Tue, 2 Oct 2007 23:26:51 +0000 Subject: [PATCH] git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@923 f3b2605a-c512-4ea7-a41b-209d697bcdaa --- doc/pair_coul.html | 124 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 124 insertions(+) create mode 100644 doc/pair_coul.html diff --git a/doc/pair_coul.html b/doc/pair_coul.html new file mode 100644 index 0000000000..8c879df247 --- /dev/null +++ b/doc/pair_coul.html @@ -0,0 +1,124 @@ +<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 coul/cut command +</H3> +<H3>pair_style coul/long command +</H3> +<P><B>Syntax:</B> +</P> +<PRE>pair_style coul/cut cutoff +pair_style coul/long cutoff +</PRE> +<UL><LI>cutoff = global cutoff for Coulombic interactions +</UL> +<P><B>Examples:</B> +</P> +<PRE>pair_style coul/cut 2.5 +pair_coeff * * +pair_coeff 2 2 3.5 +</PRE> +<PRE>pair_style coul/long 10.0 +pair_coeff * * +</PRE> +<P><B>Description:</B> +</P> +<P>The <I>coul/cut</I> style computes the standard Coulombic interaction +potential given by +</P> +<CENTER><IMG SRC = "Eqs/pair_coulomb.jpg"> +</CENTER> +<P>where C is an energy-conversion constant, Qi and Qj are the charges on +the 2 atoms, and epsilon is the dielectric constant which can be set +by the <A HREF = "dielectric.html">dielectric</A> command. The cutoff Rc truncates +the interaction distance. +</P> +<P>Style <I>coul/long</I> computes the same Coulombic interactions as style +<I>coul/cut</I> except that an additional damping factor is applied so it +can be used in conjunction with the <A HREF = "kspace_style.html">kspace_style</A> +command and its <I>ewald</I> or <I>pppm</I> option. The Coulombic cutoff +specified for this style means that pairwise interactions within this +distance are computed directly; interactions outside that distance are +computed in reciprocal space. +</P> +<P>These potentials are designed to be combined with other pair +potentials via the <A HREF = "pair_hybrid.html">pair_style hybrid/overlay</A> +command. This is because they have no repulsive core. Hence if they +are used by themselves, there will be no repulsion to keep two +oppositely charged particles from overlapping each other. +</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, or by mixing as described below: +</P> +<UL><LI>cutoff (distance units) +</UL> +<P>For <I>coul/cut</I>, the cutoff coefficient is optional. If it is not used +(as in som of the examples above), the default global value specified +in the pair_style command is used. +</P> +<P>For <I>coul/long</I> no cutoff can be specified for an individual I,J type +pair via the pair_coeff command. All type pairs use the same global +Coulombic cutoff specified in the pair_style command. +</P> +<HR> + +<P><B>Mixing, shift, table, tail correction, per-atom energy/stress, and +restart info</B>: +</P> +<P>For atom type pairs I,J and I != J, the cutoff distance for the +<I>coul/cut</I> style can be mixed. The default mix value is <I>geometric</I>. +See the "pair_modify" command for details. +</P> +<P>The <A HREF = "pair_modify.html">pair_modify</A> shift option is not relevant +for these pair styles. +</P> +<P>The <I>coul/long</I> style supports the <A HREF = "pair_modify.html">pair_modify</A> +table option for tabulation of the short-range portion of the +long-range Coulombic interaction. +</P> +<P>These pair styles do not support the <A HREF = "pair_modify.html">pair_modify</A> +tail option for adding long-range tail corrections to energy and +pressure. +</P> +<P>These pair styles can calculate per-atom energy and stress, as used by +the <A HREF = "compute_epair_atom.html">compute epair/atom</A>, <A HREF = "compute_stress_atom.html">compute +stress/atom</A>, and <A HREF = "dump.html">dump custom</A> +commands. +</P> +<P>These pair styles write their information to <A HREF = "restart.html">binary restart +files</A>, so pair_style and pair_coeff commands do not need +to be specified in an input script that reads a restart file. +</P> +<HR> + +<P><B>Restrictions:</B> +</P> +<P>The <I>coul/long</I> style is part of the "kspace" package. It is only +enabled if LAMMPS was built with that package (which it is by +default). See the <A HREF = "Section_start.html#2_3">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>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>, <A HREF = "pair_hybrid.html">pair_style +hybrid/overlay</A> +</P> +<P><B>Default:</B> none +</P> +</HTML> -- GitLab