# dihedral_style hybrid command

## Syntax

``` LAMMPS
dihedral_style hybrid style1 style2 ...
```

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

## Examples

``` LAMMPS
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](dihedral_coeff) command or in the data file.

In the dihedral_coeff commands, the name of a dihedral style must be
added after the dihedral type, with the remaining coefficients being
those appropriate to that style. In the example above, the 2
dihedral_coeff commands set dihedrals of dihedral type 1 to be computed
with a *harmonic* potential with coefficients 6.0, 1, 3 for K, d, n. All
other dihedral types (2-N) are computed with a *helix* potential with
coefficients 10, 10, 10 for A, B, C.

If dihedral coefficients are specified in the data file read via the
[read_data](read_data) command, then the same rule applies. E.g.
\"harmonic\" or \"helix\", must be added after the dihedral type, for
each line in the \"Dihedral Coeffs\" section, e.g.

    Dihedral Coeffs

    1 harmonic 6.0 1 3
    2 helix 10 10 10
    ...

If *class2* is one of the dihedral hybrid styles, the same rule holds
for specifying additional AngleTorsion (and EndBondTorsion, etc)
coefficients either via the input script or in the data file. I.e.
*class2* must be added to each line after the dihedral type. For lines
in the AngleTorsion (or EndBondTorsion, etc) Coeffs section of the data
file for dihedral types that are not *class2*, you must use an dihedral
style of *skip* as a placeholder, e.g.

    AngleTorsion Coeffs

    1 skip
    2 class2 1.0 1.0 1.0 3.0 3.0 3.0 30.0 50.0
    ...

Note that it is not necessary to use the dihedral style *skip* in the
input script, since AngleTorsion (or EndBondTorsion, etc) coefficients
need not be specified at all for dihedral types that are not *class2*.

A dihedral style of *none* with no additional coefficients can be used
in place of a dihedral style, either in a input script dihedral_coeff
command or in the data file, if you desire to turn off interactions for
specific dihedral types.

------------------------------------------------------------------------

## Restrictions

This dihedral style can only be used if LAMMPS was built with the
MOLECULE package. See the [Build package](Build_package) doc page for
more info.

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

## Related commands

[dihedral_coeff](dihedral_coeff)

## Default

none