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dihedral_style command

Syntax:

dihedral_style style 

Examples:

dihedral_style harmonic
dihedral_style multiharmonic 

Description:

Set the formula that LAMMPS will use to compute dihedral interactions for quadruplets of atoms. The list of atom quadruplets are specified in the data or restart file and are read in by a read_data or read_restart command. The coefficients for the formula for each dihedral type can also be specified in those files or by the dihedral_coeff command. In all the formulas to follow, phi is the torsional angle defined by the quadruplet of atoms.

Here are some important points to take note of when defining the LAMMPS dihedral coefficients in the formulas that follow so that they are compatible with other force fields:

A style of none means dihedral forces are not computed, even if dihedrals are defined.

harmonic The harmonic style uses the potential

K, d, and n are coefficients defined for each dihedral type.

The charmm style uses the potential

K, d, and n are coefficients defined for each dihedral type. Additionally, a weighting factor if defined (see the dihedral_coeff command) which is applied to the pairwise LJ and Coulombic interaction between the 1st and 4th atom in the dihedral quadruplet.

The multiharmonic style uses the potential

A1, A2, A3, A4, and A5 are coefficients defined for each dihedral type.

Restrictions:

Dihedral styles can only be set for atom styles that allow dihedrals to be defined.

Dihedral styles are part of the "molecular" package. They are only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.

Related commands:

dihedral_coeff

Default:

dihedral_style none