improper_style distharm command — LAMMPS documentation

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# improper_style distharm command

## Syntax

    improper_style distharm

## Examples

    improper_style distharm
    improper_coeff 1 25.0 0.5

## Description

The distharm improper style uses the potential

\[E = K (d - d_0)^2\]

where \(d\) is the oriented distance between the central atom and the plane formed by the other three atoms. If the 4 atoms in an improper quadruplet (listed in the data file read by the read_data command) are ordered I,J,K,L then the L-atom is assumed to be the central atom. Note that this is different from the convention used in the improper_style distance. The distance \(d\) is oriented and can take on negative values. This may lead to unwanted behavior if \(d_0\) is not equal to zero.

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:

- \(K\) (energy/distance^2)

- \(d_0\) (distance)

## Restrictions

This improper style can only be used if LAMMPS was built with the YAFF package. See the Build package doc page for more info.

## Related commands

improper_coeff

## Default

none