"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 cosine/periodic command :h3

[Syntax:]

angle_style cosine/periodic :pre

[Examples:]

angle_style cosine/periodic
angle_coeff * 75.0 1 6 :pre

[Description:]

The {cosine/periodic} angle style uses the following potential, which
is commonly used in the "DREIDING"_Section_howto.html#4_4 force field,
particularly for organometallic systems where {n} = 4 might be used
for an octahedral complex and {n} = 3 might be used for a trigonal
center:

:c,image(Eqs/angle_cosine_periodic.jpg)

where C, B and n are coefficients defined for each angle type.

See "(Mayo)"_#Mayo for a description of the DREIDING force field

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:

C (energy)
B = 1 or -1
n = 1, 2, 3, 4, 5 or 6 for periodicity :ul

Note that the prefactor C is specified and not the overall force
constant K = C / n^2.  When B = 1, it leads to a minimum for the
linear geometry.  When B = -1, it leads to a maximum for the linear
geometry.

[Restrictions:]

This angle style can only be used if LAMMPS was built with the
"molecular" package (which it is by default).  See the "Making
LAMMPS"_Section_start.html#2_3 section for more info on packages.

[Related commands:]

"angle_coeff"_angle_coeff.html

[Default:] none

:line

:link(Mayo)
[(Mayo)] Mayo, Olfason, Goddard III, J Phys Chem, 94, 8897-8909
(1990).
