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>dihedral_style charmm command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>dihedral_style charmm
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>dihedral_style charmm
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dihedral_coeff 1 120.0 1 60 0.5
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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>charmm</I> dihedral style uses the potential
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</P>
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<CENTER><IMG SRC = "Eqs/dihedral_charmm.jpg">
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</CENTER>
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2006-09-28 03:12:31 +08:00
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<P>See <A HREF = "#MacKerell">(MacKerell)</A> for a description of the CHARMM force
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field.
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</P>
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2006-09-22 00:22:34 +08:00
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<P>The following coefficients must be defined for each dihedral type via the
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<A HREF = "dihedral_coeff.html">dihedral_coeff</A> command as in the example above, or in
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the data file or restart files read by the <A HREF = "read_data.html">read_data</A>
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or <A HREF = "read_restart.html">read_restart</A> commands:
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</P>
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<UL><LI>K (energy)
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<LI>n (integer >= 0)
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<LI>d (integer value of degrees)
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<LI>weighting factor (0.0 to 1.0)
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</UL>
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<P>The weighting factor is applied to pairwise interaction between the
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1st and 4th atoms in the dihedral. Note that this weighting factor is
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unrelated to the weighting factor specified by the <A HREF = "doc/special_bonds.html">special
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bonds</A> command which applies to all 1-4
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interactions in the system. For CHARMM force fields, the latter
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should typically be set to 0.0, else the 1-4 interactions in a
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dihedral will be computed twice (once by the pair potential, and once
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by the dihedral/charmm potential).
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</P>
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2006-09-28 03:12:31 +08:00
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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 = "dihedral_coeff.html">dihedral_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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2006-09-28 03:12:31 +08:00
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<HR>
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<A NAME = "MacKerell"></A>
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<P><B>(MacKerell)</B> MacKerell, Bashford, Bellott, Dunbrack, Evanseck, Field,
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Fischer, Gao, Guo, Ha, et al, J Phys Chem, 102, 3586 (1998).
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</P>
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2006-09-22 00:22:34 +08:00
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</HTML>
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