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### fix manifoldforce command

Syntax:

    fix ID group-ID manifoldforce manifold manifold-args ...

- ID, group-ID are documented in fix command
- manifold = name of the manifold
- manifold-args = parameters for the manifold

Examples:

fix constrain all manifoldforce sphere 5.0

Description:

This fix subtracts each time step from the force the component along the normal of the specified manifold. This can be used in combination with minimize to remove overlap between particles while keeping them (roughly) constrained to the given manifold, e.g. to set up a run with fix nve/manifold/rattle. I have found that only hftn and quickmin with a very small time step perform adequately though.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is invoked during energy minimization.

Restrictions:

This fix is part of the USER-MANIFOLD package. It is only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.

Only use this with min_style hftn or min_style quickmin. If not, the constraints will not be satisfied very well at all. A warning is generated if the min_style is incompatible but no error.

Related commands:

fix nve/manifold/rattle, fix nvt/manifold/rattle