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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.
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:]
Angle styles can only be set for atom styles that allow angles to be
defined.
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
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