angle_style class2 command

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.

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)

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)

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)

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 for more info.

Related commands:

angle_coeff

Default: none