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.
See (Sun) for a description of the COMPASS class2 force field.
For this style, coefficients for the Ed formula can be specified in either the input script or data file. These are the 6 coefficients:
Coefficients for all the other formulas can only 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:
This dihedral style can only be used if LAMMPS was built with the "class2" package. See the Making LAMMPS section for more info on packages.
Related commands:
Default: none
(Sun) Sun, J Phys Chem B 102, 7338-7364 (1998).