forked from lijiext/lammps
76 lines
2.7 KiB
HTML
76 lines
2.7 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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<H3>improper_style hybrid command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>improper_style hybrid style1 style2 ...
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</PRE>
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<UL><LI>style1,style2 = list of one or more improper styles
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>improper_style hybrid harmonic helix
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improper_coeff 1 harmonic 120.0 30
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improper_coeff 2 cvff 20.0 -1 2
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>The <I>hybrid</I> style enables the use of multiple improper styles in one
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simulation. An improper style is assigned to each improper type. For
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example, impropers in a polymer flow (of improper type 1) could be
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computed with a <I>harmonic</I> potential and impropers in the wall
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boundary (of improper type 2) could be computed with a <I>cvff</I>
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potential. The assignment of improper type to style is made via the
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<A HREF = "improper_coeff.html">improper_coeff</A> command or in the data file.
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</P>
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<P>In the improper_coeff command, the first coefficient sets the improper
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style and the remaining coefficients are those appropriate to that
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style. In the example above, the 2 improper_coeff commands would set
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impropers of improper type 1 to be computed with a <I>harmonic</I>
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potential with coefficients 120.0, 30 for K, X0. Improper type 2
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would be computed with a <I>cvff</I> potential with coefficients 20.0, -1,
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2 for K, d, n.
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</P>
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<P>If the improper <I>class2</I> potential is one of the hybrid styles, it
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requires additional AngleAngle coefficients be specified in the data
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file. These lines must also have an additional "class2" argument
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added after the improper type. For improper types which are assigned
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to other hybrid styles, use the style name (e.g. "harmonic")
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appropriate to that style. The AngleAngle coeffs for that improper
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type will then be ignored.
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</P>
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<P>An improper style of <I>none</I> can be specified as the 2nd argument to
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the improper_coeff command, if you desire to turn off certain improper
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types.
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</P>
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<HR>
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<P><B>Restrictions:</B>
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</P>
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<P>This improper style can only be used if LAMMPS was built with the
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MOLECULAR package (which it is by default). See the <A HREF = "Section_start.html#start_3">Making
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LAMMPS</A> section for more info on packages.
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</P>
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<P>Unlike other improper styles, the hybrid improper style does not store
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improper coefficient info for individual sub-styles in a <A HREF = "restart.html">binary
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restart files</A>. Thus when retarting a simulation from a
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restart file, you need to re-specify improper_coeff commands.
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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 = "improper_coeff.html">improper_coeff</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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