Syntax:
dihedral_style class2
Examples:
dihedral_style class2 dihedral_coeff 1 100 75 100 70 80 60
Description:
The class2 dihedral style uses the potential
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.
For this style, only coefficients for the Ed formula can be specified in the input script. These are the 6 coefficients:
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:
For the Eebt formula, the coefficients are listed under a "EndBondTorsion Coeffs" heading and each line lists 8 coefficients:
For the Eat formula, the coefficients are listed under a "AngleTorsion Coeffs" heading and each line lists 8 coefficients:
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:
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:
Restrictions:
Dihedral styles can only be set for atom styles that allow dihedrals to be defined.
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 for more info.
Related commands:
Default: none