forked from lijiext/lammps
92 lines
3.3 KiB
HTML
92 lines
3.3 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_coeff 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_coeff N args
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</PRE>
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<UL><LI>N = improper type (see asterisk form below)
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<LI>args = coefficients for one or more improper types
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>improper_coeff 1 300.0 0.0
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improper_coeff * 80.2 -1 2
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improper_coeff *4 80.2 -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>Specify the improper force field coefficients for one or more improper
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types. The number and meaning of the coefficients depends on the
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improper style. Improper coefficients can also be set in the data
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file read by the <A HREF = "read_data.html">read_data</A> command or in a restart
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file.
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</P>
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<P>N can be specified in one of two ways. An explicit numeric value can
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be used, as in the 1st example above. Or a wild-card asterisk can be
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used to set the coefficients for multiple improper types. This takes
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the form "*" or "*n" or "n*" or "m*n". If N = the number of improper
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types, then an asterisk with no numeric values means all types from 1
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to N. A leading asterisk means all types from 1 to n (inclusive). A
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trailing asterisk means all types from n to N (inclusive). A middle
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asterisk means all types from m to n (inclusive).
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</P>
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<P>Note that using an improper_coeff command can override a previous
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setting for the same improper type. For example, these commands set
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the coeffs for all improper types, then overwrite the coeffs for just
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improper type 2:
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</P>
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<PRE>improper_coeff * 300.0 0.0
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improper_coeff 2 50.0 0.0
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</PRE>
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<P>A line in a data file that specifies improper coefficients uses the
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exact same format as the arguments of the improper_coeff command in an
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input script, except that wild-card asterisks should not be used since
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coefficients for all N types must be listed in the file. For example,
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under the "Improper Coeffs" section of a data file, the line that
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corresponds to the 1st example above would be listed as
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</P>
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<PRE>1 300.0 0.0
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</PRE>
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<HR>
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<P>Here is an alphabetic list of improper styles defined in LAMMPS. Click on
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the style to display the formula it computes and coefficients
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specified by the associated <A HREF = "improper_coeff.html">improper_coeff</A> command:
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</P>
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<UL><LI><A HREF = "improper_style_none.html">improper_style none</A> - turn off improper interactions
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<LI><A HREF = "improper_style_hybrid.html">improper_style hybrid</A> - define multiple styles of improper interactions
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</UL>
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<UL><LI><A HREF = "improper_style_class2.html">improper_style class2</A> - COMPASS (class 2) improper
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<LI><A HREF = "improper_style_cvff.html">improper_style cvff</A> - CVFF improper
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<LI><A HREF = "improper_style_harmonic.html">improper_style harmonic</A> - harmonic improper
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</UL>
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<HR>
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<P><B>Restrictions:</B>
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</P>
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<P>This command must come after the simulation box is defined by a
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<A HREF = "read_data.html">read_data</A>, <A HREF = "read_restart.html">read_restart</A>, or
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<A HREF = "create_box.html">create_box</A> command.
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</P>
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<P>An improper style must be defined before any improper coefficients are
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set, either in the input script or in a data file.
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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_style.html">improper_style</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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