bond_style hybrid command

Syntax

bond_style hybrid style1 style2 ...
  • style1,style2 = list of one or more bond styles

Examples

bond_style hybrid harmonic fene
bond_coeff 1 harmonic 80.0 1.2
bond_coeff 2* fene 30.0 1.5 1.0 1.0

Description

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

In the bond_coeff commands, the name of a bond style must be added after the bond type, with the remaining coefficients being those appropriate to that style. In the example above, the 2 bond_coeff commands set bonds of bond type 1 to be computed with a harmonic potential with coefficients 80.0, 1.2 for K, r0. All other bond types (2-N) are computed with a fene potential with coefficients 30.0, 1.5, 1.0, 1.0 for K, R0, epsilon, sigma.

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

Bond Coeffs

1 harmonic 80.0 1.2
2 fene 30.0 1.5 1.0 1.0
...

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


Restrictions

This bond 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 bond styles, the hybrid bond style does not store bond 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 bond_coeff commands.