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lammps/doc/dihedral_style_class2.txt
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dihedral_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
dihedral_style class2 command :h3
[Syntax:]
dihedral_style class2 :pre
[Examples:]
dihedral_style class2
dihedral_coeff 1 100 75 100 70 80 60 :pre
[Description:]
The {class2} dihedral style uses the potential
:c,image(Eqs/dihedral_class2.jpg)
where Ed is the dihedral term, Embt is a middle-bond-torsion term,
Eebt is an end-bond-torsion term, Eat is an angle-torsion term, Eaat
is an angle-angle-torsion term, and Ebb13 is a bond-bond-13 term.
Theta1 and theta2 are equilibrium angles and r1 r2 r3 are equilibrium
bond lengths.
See "(Sun)"_#Sun for a description of the COMPASS class2 force field.
For this style, only coefficients for the Ed formula can be specified
in the input script. These are the 6 coefficients:
K1 (energy)
phi1 (degrees)
K2 (energy)
phi2 (degrees)
K3 (energy)
phi3 (degrees) :ul
Coefficients for all the other formulas must be specified in the data
file.
For the Embt formula, the coefficients are listed under a
"MiddleBondTorsion Coeffs" heading and each line lists 4 coefficients:
A1 (energy/distance)
A2 (energy/distance)
A3 (energy/distance)
r2 (distance) :ul
For the Eebt formula, the coefficients are listed under a
"EndBondTorsion Coeffs" heading and each line lists 8 coefficients:
B1 (energy/distance)
B2 (energy/distance)
B3 (energy/distance)
C1 (energy/distance)
C2 (energy/distance)
C3 (energy/distance)
r1 (distance)
r3 (distance) :ul
For the Eat formula, the coefficients are listed under a "AngleTorsion
Coeffs" heading and each line lists 8 coefficients:
D1 (energy/radian)
D2 (energy/radian)
D3 (energy/radian)
E1 (energy/radian)
E2 (energy/radian)
E3 (energy/radian)
theta1 (degrees)
theta2 (degrees) :ul
Theta1 and theta2 are specified in degrees, but LAMMPS converts them
to radians internally; hence the units of D and E are in
energy/radian.
For the Eaat formula, the coefficients are listed under a
"AngleAngleTorsion Coeffs" heading and each line lists 3 coefficients:
M (energy/radian^2)
theta1 (degrees)
theta2 (degrees) :ul
Theta1 and theta2 are specified in degrees, but LAMMPS converts them
to radians internally; hence the units of M are in energy/radian^2.
For the Ebb13 formula, the coefficients are listed under a "BondBond13
Coeffs" heading and each line lists 3 coefficients:
N (energy/distance^2)
r1 (distance)
r3 (distance) :ul
[Restrictions:]
This dihedral 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:]
"dihedral_coeff"_dihedral_coeff.html
[Default:] none
:line
:link(Sun)
[(Sun)] Sun, J Phys Chem B 102, 7338-7364 (1998).
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