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lammps/doc/angle_style_class2.txt
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angle_style_class2.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 class2 command :h3
[Syntax:]
angle_style class2 :pre
[Examples:]
angle_style class2
angle_coeff * 75.0 :pre
[Description:]
The {class2} angle style uses the potential
:c,image(Eqs/angle_class2.jpg)
where Ea is the angle term, Ebb is a bond-bond term, and Eba is a
bond-angle term. Theta0 is the equilibrium angle and r1 and r2 are
the equilibrium bond lengths.
See "(Sun)"_#Sun for a description of the COMPASS class2 force field.
For this style, only coefficients for the Ea formula can be specified
in the input script. These are the 4 coefficients:
theta0 (degrees)
K2 (energy/radian^2)
K3 (energy/radian^2)
K4 (energy/radian^2) :ul
Theta0 is specified in degrees, but LAMMPS converts it to radians
internally; hence the units of K are in energy/radian^2.
Coefficients for the Ebb and Eba formulas must be specified in the
data file.
For the Ebb formula, the coefficients are listed under a "BondBond
Coeffs" heading and each line lists 3 coefficients:
M (energy/distance^2)
r1 (distance)
r2 (distance) :ul
For the Eba formula, the coefficients are listed under a "BondAngle
Coeffs" heading and each line lists 4 coefficients:
N1 (energy/distance^2)
N2 (energy/distance^2)
r1 (distance)
r2 (distance) :ul
The theta0 value in the Eba formula is not specified, since it is the
same value from the Ea formula.
[Restrictions:]
This angle style is part of the "class2" package. It is only enabled
if LAMMPS was built with that package. See the "Making
LAMMPS"_Section_start.html#2_2 section for more info.
[Related commands:]
"angle_coeff"_angle_coeff.html
[Default:] none
:line
:link(Sun)
[(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).
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