# improper_style distance command¶

## Syntax¶

improper_style distance


## Examples¶

improper_style distance
improper_coeff 1 80.0 100.0


## Description¶

The distance improper style uses the potential

$E = K_2 d^2 + K_4 d^4$

where $$d$$ is the 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 I-atom is assumed to be the central atom.

Note that defining 4 atoms to interact in this way, does not mean that bonds necessarily exist between I-J, J-K, or K-L, as they would in a linear dihedral. Normally, the bonds I-J, I-K, I-L would exist for an improper to be defined between the 4 atoms.

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:

• $$K_2$$ (energy/distance^2)

• $$K_4$$ (energy/distance^4)

## Restrictions¶

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

none