mirror of https://github.com/lammps/lammps.git
70 lines
2.5 KiB
HTML
70 lines
2.5 KiB
HTML
<HTML>
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<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>
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</CENTER>
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<HR>
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<H3>fix wall/lj126 command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>fix ID group-ID wall/lj126 style coord epsilon sigma cutoff
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</PRE>
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<UL><LI>ID, group-ID are documented in <A HREF = "fix.html">fix</A> command
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<LI>wall/lj126 = style name of this fix command
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<LI>style = <I>xlo</I> or <I>xhi</I> or <I>ylo</I> or <I>yhi</I> or <I>zlo</I> or <I>zhi</I>
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<LI>coord = position of wall
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<LI>epsilon = Lennard-Jones epsilon for wall-particle interaction
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<LI>sigma = Lennard-Jones sigma for wall-particle interaction
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<LI>cutoff = distance from wall at which wall-particle interaction is cut off
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>fix wallhi all wall/lj126 xhi 10.0 1.0 1.0 1.12
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Bound the simulation domain with a Lennard-Jones wall that encloses
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the atoms. The energy E of a wall-particle interactions is given by
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the 12-6 potential
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</P>
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<CENTER><IMG SRC = "Eqs/pair_lj.jpg">
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</CENTER>
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<P>where <I>r</I> is the distance from the particle to the wall <I>coord</I>, and
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epsilon and sigma are the usual LJ parameters. Rc is the cutoff value
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specified in the command. This interaction provides a harder, more
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repulsive interaction with the wall than the softer 9-3 potential
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provided by the <A HREF = "fix_wall_lj93.html">fix wall/lj93</A> command.
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</P>
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<P>The wall potential is shifted so that the energy of a wall-particle
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interaction is 0.0 at the cutoff distance.
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</P>
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<P>This fix supports the <A HREF = "fix_modify.html">fix_modify</A> options for
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<I>thermo</I> and <I>energy</I>. The former will print the contribution the fix
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makes to the energy of the system when thermodynamics is printed,
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where the energy of each particle comes from the integrated form of
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the equation above. The latter will add this contribution to the
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total potential energy (PotEng).
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</P>
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<P>The forces due to this fix are also imposed during an energy
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minimization, invoked by the <A HREF = "minimize.html">minimize</A> command. If you
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want that energy to be included in the total potential energy of the
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system (the quantity being minimized), you must enable the
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<A HREF = "fix_modify.html">fix_modify</A> <I>energy</I> option for this fix.
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</P>
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<P><B>Restrictions:</B> none
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "fix_wall_reflect.html">fix wall/reflect</A>, <A HREF = "fix_wall_lj93.html">fix
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wall/lj93</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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