2006-09-22 00:22:34 +08:00
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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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<HR>
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<H3>boundary command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>boundary x y z
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</PRE>
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<UL><LI>x,y,z = <I>p</I> or <I>s</I> or <I>f</I> or <I>m</I>, one or two letters
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<PRE> <I>p</I> is periodic
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<I>f</I> is non-periodic and fixed
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<I>s</I> is non-periodic and shrink-wrapped
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<I>m</I> is non-periodic and shrink-wrapped with a minimum value
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>boundary p p f
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boundary p fs p
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boundary s f fm
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Set the style of boundaries for the global simulation box in each
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dimension. A single letter assigns the same style to both the lower
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and upper face of the box. Two letters assigns the first style to the
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lower face and the second style to the upper face. The initial size
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of the simulation box is set by the <A HREF = "read_data.html">read_data</A>,
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<A HREF = "read_restart.html">read_restart</A>, or <A HREF = "create_box.html">create_box</A>
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commands.
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</P>
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<P>The style <I>p</I> means the box is periodic, so that particles interact
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across the boundary, and they can exit one end of the box and re-enter
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the other end. A periodic dimension can change in size due to
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2010-04-03 00:51:06 +08:00
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constant pressure boundary conditions or box deformation (see the <A HREF = "fix_nh.html">fix
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2007-06-20 20:56:25 +08:00
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npt</A> and <A HREF = "fix_deform.html">fix deform</A> commands). The <I>p</I>
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style must be applied to both faces of a dimension.
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2006-09-22 00:22:34 +08:00
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</P>
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<P>The styles <I>f</I>, <I>s</I>, and <I>m</I> mean the box is non-periodic, so that
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particles do not interact across the boundary and do not move from one
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side of the box to the other. For style <I>f</I>, the position of the face
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is fixed. If an atom moves outside the face it may be lost. For
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style <I>s</I>, the position of the face is set so as to encompass the
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atoms in that dimension (shrink-wrapping), no matter how far they
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move. For style <I>m</I>, shrink-wrapping occurs, but is bounded by the
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value specified in the data or restart file or set by the
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<A HREF = "create_box.html">create_box</A> command. For example, if the upper z
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face has a value of 50.0 in the data file, the face will always be
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positioned at 50.0 or above, even if the maximum z-extent of all the
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atoms becomes less than 50.0.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This command cannot be used after the simulation box is defined by a
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<A HREF = "read_data.html">read_data</A> or <A HREF = "create_box.html">create_box</A> command.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P>See the <A HREF = "thermo_modify.html">thermo_modify</A> command for a discussion
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of lost atoms.
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</P>
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<P><B>Default:</B>
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</P>
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<PRE>boundary p p p
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</PRE>
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</HTML>
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