# pair_style kolmogorov/crespi/full command

## Syntax

pair_style hybrid/overlay kolmogorov/crespi/full cutoff tap_flag


cutoff = global cutoff (distance units) tap_flag = 0/1 to turn off/on the taper function

## Examples

pair_style hybrid/overlay kolmogorov/crespi/full 20.0 0
pair_coeff * * none
pair_coeff * * kolmogorov/crespi/full  CH.KC   C C

pair_style hybrid/overlay rebo kolmogorov/crespi/full 16.0 1
pair_coeff * * rebo                    CH.airebo    C H
pair_coeff * * kolmogorov/crespi/full  CH_taper.KC  C H


## Description

The kolmogorov/crespi/full style computes the Kolmogorov-Crespi (KC) interaction potential as described in (Kolmogorov). No simplification is made,

It is important to have a sufficiently large cutoff to ensure smooth forces and to include all the pairs to build the neighbor list for calculating the normals. Energies are shifted so that they go continuously to zero at the cutoff assuming that the exponential part of Vij (first term) decays sufficiently fast. This shift is achieved by the last term in the equation for Vij above. This is essential only when the tapper function is turned off. The formula of taper function can be found in pair style ilp/graphene/hbn.

Note

This potential is intended for interactions between two different graphene layers. Therefore, to avoid interaction within the same layers, each layer should have a separate molecule id and is recommended to use “full” atom style in the data file.

The parameter file (e.g. CH.KC), is intended for use with metal units, with energies in meV. Two additional parameters, S, and rcut are included in the parameter file. S is designed to facilitate scaling of energies. rcut is designed to build the neighbor list for calculating the normals for each atom pair.

Note

Two new sets of parameters of KC potential for hydrocarbons, CH.KC (without the taper function) and CH_taper.KC (with the taper function) are presented in (Ouyang). The energy for the KC potential with the taper function goes continuously to zero at the cutoff. The parameters in both CH.KC and CH_taper.KC provide a good description in both short- and long-range interaction regimes. While the original parameters (CC.KC) published in (Kolmogorov) are only suitable for long-range interaction regime. This feature is essential for simulations in high pressure regime (i.e., the interlayer distance is smaller than the equilibrium distance). The benchmark tests and comparison of these parameters can be found in (Ouyang).

This potential must be used in combination with hybrid/overlay. Other interactions can be set to zero using pair_style none.

Mixing, shift, table, tail correction, restart, rRESPA info:

This pair style does not support the pair_modify mix, shift, table, and tail options.

This pair style does not write their information to binary restart files, since it is stored in potential files. Thus, you need to re-specify the pair_style and pair_coeff commands in an input script that reads a restart file.

## Restrictions

This fix is part of the USER-MISC package. It is only enabled if LAMMPS was built with that package. See the Build package doc page for more info.

This pair potential requires the newton setting to be on for pair interactions.

The CH.KC potential file provided with LAMMPS (see the potentials folder) are parameterized for metal units. You can use this potential with any LAMMPS units, but you would need to create your own custom CC.KC potential file with all coefficients converted to the appropriate units.