Syntax:
angle_style class2
Examples:
angle_style class2 angle_coeff * 75.0
Description:
The class2 angle style uses the potential
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) 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 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:
For the Eba formula, the coefficients are listed under a "BondAngle Coeffs" heading and each line lists 4 coefficients:
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 for more info.
Related commands:
Default: none
(Sun) Sun, J Phys Chem B 102, 7338-7364 (1998).