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lammps/doc/angle_quartic.txt
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"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)
:line
angle_style quartic command :h3
angle_style quartic/omp 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.
:line
Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
the same as the corresponding style without the suffix. They have
been optimized to run faster, depending on your available hardware, as
discussed in "Section_accelerate"_Section_accelerate.html of the
manual. The accelerated styles take the same arguments and should
produce the same results, except for round-off and precision issues.
These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
packages, respectively. They are only enabled if LAMMPS was built with
those packages. See the "Making LAMMPS"_Section_start.html#start_3
section for more info.
You can specify the accelerated styles explicitly in your input script
by including their suffix, or you can use the "-suffix command-line
switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
use the "suffix"_suffix.html command in your input script.
See "Section_accelerate"_Section_accelerate.html of the manual for
more instructions on how to use the accelerated styles effectively.
:line
[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
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