improper_style distharm command
improper_style distharm improper_coeff 1 25.0 0.5
The distharm improper style uses the potential
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:
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.