forked from lijiext/lammps
66 lines
2.1 KiB
HTML
66 lines
2.1 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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<HR>
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<H3>angle_style cg/cmm command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>angle_style cg/cmm
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>angle_style cg/cmm
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angle_coeff 1 300.0 107.0 lj9_6 0.4491 3.7130
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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>cg/cmm</I> angle style is a combination of the harmonic angle potential,
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</P>
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<CENTER><IMG SRC = "Eqs/angle_harmonic.jpg">
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</CENTER>
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<P>where theta0 is the equilibrium value of the angle and K a prefactor,
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with the <I>repulsive</I> part of the non-bonded <I>cg/cmm</I> pair style
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between the atoms 1 and 3. This angle potential is intended for
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coarse grained MD simulations with the CMM parametrization using the
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<A HREF = "pair_cmm.html">pair_style cg/cmm</A>. Relative to the pair_style
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<I>cg/cmm</I>, however, the energy is shifted by <I>epsilon</I>, to avoid sudden
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jumps. Note that the usual 1/2 factor is included in K.
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</P>
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<P>The following coefficients must be defined for each angle type via the
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<A HREF = "angle_coeff.html">angle_coeff</A> command as in the example above. As
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with other CMM coarse grained parameters, they cannot be set in the
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data file, but can be restored from restarts via the
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<A HREF = "read_restart.html">read_restart</A> command:
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</P>
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<UL><LI>K (energy/radian^2)
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<LI>theta0 (degrees)
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<LI>cg_type (string, one of lj9_6, lj12_4, lj12_6)
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<LI>epsilon (energy units)
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<LI>sigma (distance units)
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</UL>
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<P>Theta0 is specified in degrees, but LAMMPS converts it to radians
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internally; hence the units of K are in energy/radian^2.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This angle style can only be used if LAMMPS was built with the
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"user-cg-cmm" package. See the <A HREF = "Section_start.html#2_3">Making LAMMPS</A> section
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for more info on packages.
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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 = "angle_coeff.html">angle_coeff</A>, <A HREF = "angle_harmonic.html">angle_style
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harmonic</A>, <A HREF = "pair_cmm.html">pair_style cg/cmm</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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