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improper_style inversion/harmonic command

Syntax:

improper_style inversion/harmonic 

Examples:

improper_style inversion/harmonic
improper_coeff 1 18.776340 0.000000 

Description:

The inversion/harmonic improper style follows the Wilson-Decius out-of-plane angle definition and uses an harmonic potential:

where K is the force constant and omega is the angle evaluated for all three axis-plane combinations centered around the atom I. For the IL axis and the IJK plane omega looks as follows:

Note that the inversion/harmonic angle term evaluation differs to the improper_umbrella due to the cyclic evaluation of all possible angles omega.

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

If omega0 = 0 the potential term has a minimum for the planar structure. Otherwise it has two minima at +/- omega0, with a barrier in between.


Restrictions:

This improper style can only be used if LAMMPS was built with the USER-MOFFF package. See the Making LAMMPS section for more info on packages.

Related commands:

improper_coeff

Default: none