\(\renewcommand{\AA}{\text{Å}}\)

# dihedral_style cosine/squared/restricted command

## Syntax

    dihedral_style cosine/squared/restricted

## Examples

    dihedral_style cosine/squared/restricted
    dihedral_coeff 1 10.0 120

## Description

Added in version 17Apr2024.

The cosine/squared/restricted dihedral style uses the potential

\[E = K [\cos(\phi) - \cos(\phi_0)]^2 / \sin^2(\phi)\]

, which is commonly used in the MARTINI force field.

See (Bulacu) for a description of the restricted dihedral for the MARTINI force field.

The following coefficients must be defined for each dihedral type via the dihedral_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

- \(K\) (energy)

- \(\phi_0\) (degrees)

\(\phi_0\) is specified in degrees, but LAMMPS converts it to radians internally.

## Restrictions

This dihedral style can only be used if LAMMPS was built with the EXTRA-MOLECULE package. See the Build package doc page for more info.

## Related commands

dihedral_coeff

## Default

none

(Bulacu) Bulacu, Goga, Zhao, Rossi, Monticelli, Periole, Tieleman, Marrink, J Chem Theory Comput, 9, 3282-3292 (2013).