forked from lijiext/lammps
80 lines
1.8 KiB
Plaintext
80 lines
1.8 KiB
Plaintext
"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).
|