forked from lijiext/lammps
75 lines
2.8 KiB
HTML
75 lines
2.8 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>dihedral_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>dihedral_style hybrid style1 style2 ...
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</PRE>
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<UL><LI>style1,style2 = list of one or more dihedral styles
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>dihedral_style hybrid harmonic helix
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dihedral_coeff 1 harmonic 6.0 1 3
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dihedral_coeff 2 helix 10 10 10
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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 dihedral styles in one
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simulation. An dihedral style is assigned to each dihedral type. For
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example, dihedrals in a polymer flow (of dihedral type 1) could be
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computed with a <I>harmonic</I> potential and dihedrals in the wall
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boundary (of dihedral type 2) could be computed with a <I>helix</I>
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potential. The assignment of dihedral type to style is made via the
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<A HREF = "dihedral_coeff.html">dihedral_coeff</A> command or in the data file.
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</P>
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<P>In the dihedral_coeff command, the first coefficient sets the dihedral
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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 dihedral_coeff commands would set
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dihedrals of dihedral type 1 to be computed with a <I>harmonic</I>
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potential with coefficients 80.0, 1.2 for K, d, n. Dihedral type 2
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would be computed with a <I>helix</I> potential with coefficients 10.0,
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10.0, 10.0 for A, B, C.
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</P>
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<P>If the dihedral <I>class2</I> potential is one of the hybrid styles, it
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requires additional MiddleBondTorsion, EndBondTorsion, AngleTorsion,
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AngleAngleTorsion, and BondBond13 coefficients be specified in the
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data file. These lines must also have an additional "class2" argument
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added after the dihedral type. For dihedral 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 MiddleBondTorsion, etc coeffs for that
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dihedral type will then be ignored.
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</P>
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<P>A dihedral style of <I>none</I> can be specified as the 2nd argument to the
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dihedral_coeff command, if you desire to turn off certain dihedral
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types.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This dihedral 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#2_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 dihedral styles, the hybrid dihedral style does not store
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dihedral 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 dihedral_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 = "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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</HTML>
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