angle_style hybrid command

Syntax

angle_style hybrid style1 style2 ...
  • style1,style2 = list of one or more angle styles

Examples

angle_style hybrid harmonic cosine
angle_coeff 1 harmonic 80.0 30.0
angle_coeff 2* cosine 50.0

Description

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

In the angle_coeff commands, the name of an angle style must be added after the angle type, with the remaining coefficients being those appropriate to that style. In the example above, the 2 angle_coeff commands set angles of angle type 1 to be computed with a harmonic potential with coefficients 80.0, 30.0 for K, theta0. All other angle types (2-N) are computed with a cosine potential with coefficient 50.0 for K.

If angle coefficients are specified in the data file read via the read_data command, then the same rule applies. E.g. “harmonic” or “cosine”, must be added after the angle type, for each line in the “Angle Coeffs” section, e.g.

Angle Coeffs

1 harmonic 80.0 30.0
2 cosine 50.0
...

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

BondBond Coeffs

1 skip
2 class2 3.6512 1.0119 1.0119
...

Note that it is not necessary to use the angle style skip in the input script, since BondBond (or BondAngle) coefficients need not be specified at all for angle types that are not class2.

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


Restrictions

This angle style can only be used if LAMMPS was built with the MOLECULE package. See the Making LAMMPS section for more info on packages.

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