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### dihedral_style hybrid command

Syntax:

    dihedral_style hybrid style1 style2 ...

- style1,style2 = list of one or more dihedral styles

Examples:

    dihedral_style hybrid harmonic helix
    dihedral_coeff 1 harmonic 6.0 1 3
    dihedral_coeff 2 helix 10 10 10

Description:

The hybrid style enables the use of multiple dihedral styles in one simulation. An dihedral style is assigned to each dihedral type. For example, dihedrals in a polymer flow (of dihedral type 1) could be computed with a harmonic potential and dihedrals in the wall boundary (of dihedral type 2) could be computed with a helix potential. The assignment of dihedral type to style is made via the dihedral_coeff command or in the data file.

In the dihedral_coeff command, the first coefficient sets the dihedral style and the remaining coefficients are those appropriate to that style. In the example above, the 2 dihedral_coeff commands would set dihedrals of dihedral type 1 to be computed with a harmonic potential with coefficients 80.0, 1.2 for K, d, n. Dihedral type 2 would be computed with a helix potential with coefficients 10.0, 10.0, 10.0 for A, B, C.

If the dihedral class2 potential is one of the hybrid styles, it requires additional MiddleBondTorsion, EndBondTorsion, AngleTorsion, AngleAngleTorsion, and BondBond13 coefficients be specified in the data file. These lines must also have an additional "class2" argument added after the dihedral type. For dihedral types which are assigned to other hybrid styles, use the style name (e.g. "harmonic") appropriate to that style. The MiddleBondTorsion, etc coeffs for that dihedral type will then be ignored.

A dihedral style of none can be specified as the 2nd argument to the dihedral_coeff command, if you desire to turn off certain dihedral types.

Restrictions:

This dihedral style can only be used if LAMMPS was built with the "molecular" package (which it is by default). See the Making LAMMPS section for more info on packages.

Unlike other dihedral styles, the hybrid dihedral style does not store dihedral coefficient info for individual sub-styles in a binary restart files. Thus when retarting a simulation from a restart file, you need to re-specify dihedral_coeff commands.

Related commands:

dihedral_coeff

Default: none