# 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 USER-YAFF package. See the Build package doc page for more info.

none