"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)
:link(ld,Manual.html)
:link(lc,Section_commands.html#comm)

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improper_style distance command :h3

[Syntax:]

improper_style distance

[Examples:]

improper_style distance
improper_coeff 1 80.0 100.0 :pre

[Description:]

The {distance} improper style uses the potential

:c,image(Eqs/improper_dist-1.jpg)

where d is the distance between the central atom and the plane formed
by the other three atoms.  If the 4 atoms in an improper quadruplet
(listed in the data file read by the "read_data"_read_data.html
command) are ordered I,J,K,L then the I-atom is assumed to be the
central atom.

:c,image(JPG/improper_distance.jpg)

Note that defining 4 atoms to interact in this way, does not mean that
bonds necessarily exist between I-J, J-K, or K-L, as they would in a
linear dihedral. Normally, the bonds I-J, I-K, I-L would exist for an
improper to be defined between the 4 atoms.

The following coefficients must be defined for each improper type via
the improper_coeff command as in the example above, or in the data
file or restart files read by the read_data or read_restart commands:

K_2 (energy/distance^2)
K_4 (energy/distance^4) :ul

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[Restrictions:]

This improper style can only be used if LAMMPS was built with the
USER-MISC package.  See the "Making LAMMPS"_Section_start.html#start_3
section for more info on packages.

[Related commands:]

"improper_coeff"_improper_coeff.html

[Default:] none