forked from lijiext/lammps
64 lines
1.8 KiB
Plaintext
64 lines
1.8 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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improper_style cvff command :h3
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[Syntax:]
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improper_style cvff :pre
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[Examples:]
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improper_style cvff
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improper_coeff 1 80.0 -1 4 :pre
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[Description:]
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The {cvff} improper style uses the potential
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:c,image(Eqs/improper_cvff.jpg)
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where phi is the Wilson out-of-plane angle.
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If the 4 atoms in an improper quadruplet (listed in the data file read
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by the "read_data"_read_data.html command) are ordered I,J,K,L then
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the Wilson angle is between the plane of I,J,K and the plane of J,K,L.
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This is essentially a dihedral angle, which is why the formula for
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this improper style is the same as for "dihedral_style
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harmonic"_dihedral_harmonic.html. Alternatively, you can think of
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atoms J,K,L as being in a plane, and atom I above the plane, and the
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Wilson angle as a measure of how far out-of-plane I is with respect to
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the other 3 atoms.
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Note that defining 4 atoms to interact in this way, does not mean that
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bonds necessarily exist between I-J, J-K, or K-L, as they would in a
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linear dihedral. Normally, the bonds I-J, I-K, I-L would exist for an
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improper to be defined between the 4 atoms.
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The following coefficients must be defined for each improper type via
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the "improper_coeff"_improper_coeff.html command as in the example
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above, or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands:
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K (energy)
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d (+1 or -1)
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n (0,1,2,3,4,6) :ul
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[Restrictions:]
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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 "Making
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LAMMPS"_Section_start.html#2_3 section for more info on packages.
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[Related commands:]
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"improper_coeff"_improper_coeff.html
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[Default:] none
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