"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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angle_style quartic command :h3

[Syntax:]

angle_style quartic :pre

[Examples:]

angle_style quartic
angle_coeff 1 129.1948 56.8726 -25.9442 -14.2221 :pre

[Description:]

The {quartic} angle style uses the potential

:c,image(Eqs/angle_quartic.jpg)

where theta0 is the equilibrium value of the angle, and K is a
prefactor.  Note that the usual 1/2 factor is included in K.

The following coefficients must be defined for each angle type via the
"angle_coeff"_angle_coeff.html command as in the example above, or in
the data file or restart files read by the "read_data"_read_data.html
or "read_restart"_read_restart.html commands:

theta0 (degrees)
K2 (energy/radian^2)
K3 (energy/radian^3)
K4 (energy/radian^4) :ul

Theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.

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[Restrictions:]

This angle 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:]

"angle_coeff"_angle_coeff.html

[Default:] none
