\(\renewcommand{\AA}{\text{Å}}\)

# pair_style coul/shield command

## Syntax

    pair_style coul/shield cutoff tap_flag

- cutoff = global cutoff (distance units)

- tap_flag = 0/1 to turn off/on the taper function

## Examples

    pair_style coul/shield 16.0 1
    pair_coeff 1 2 0.70

## Description

Style coul/shield computes a Coulomb interaction for boron and nitrogen atoms located in different layers of hexagonal boron nitride. This potential is designed be used in combination with the pair style ilp/graphene/hbn

Note

This potential is intended for electrostatic interactions between two different layers of hexagonal boron nitride. Therefore, to avoid interaction within the same layers, each layer should have a separate molecule id and is recommended to use the “full” atom style, so that charge and molecule ID information is included.

\[\begin{split}E = & \frac{1}{2} \sum_i \sum_{j \neq i} V_{ij} \\ V_{ij} = & \mathrm{Tap}(r_{ij})\frac{\kappa q_i q_j}{\sqrt[3]{r_{ij}^3+(1/\lambda_{ij})^3}}\\ \mathrm{Tap}(r_{ij}) = & 20\left ( \frac{r_{ij}}{R_{cut}} \right )^7 - 70\left ( \frac{r_{ij}}{R_{cut}} \right )^6 + 84\left ( \frac{r_{ij}}{R_{cut}} \right )^5 - 35\left ( \frac{r_{ij}}{R_{cut}} \right )^4 + 1\end{split}\]

Where Tap(\(r_{ij}\)) is the taper function which provides a continuous cutoff (up to third derivative) for inter-atomic separations larger than \(r_c\) (Leven1), (Leven2) and (Maaravi). Here \(\lambda\) is the shielding parameter that eliminates the short-range singularity of the classical mono-polar electrostatic interaction expression (Maaravi).

The shielding parameter \(\lambda\) (1/distance units) must be defined for each pair of atom types via the pair_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

The global cutoff (\(r_c\)) specified in the pair_style command is used.

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

This pair style does not support parameter mixing. Coefficients must be given explicitly for each type of particle pairs.

The pair_modify table option is not relevant for this pair style.

This pair style does not support the pair_modify tail option for adding long-range tail corrections to energy and pressure.

This pair style can only be used via the pair keyword of the run_style respa command. It does not support the inner, middle, outer keywords.

## Restrictions

This pair style is part of the INTERLAYER package. It is only enabled if LAMMPS was built with that package. See the Build package page for more info.

## Related commands

pair_coeff pair_style ilp/graphene/hbn

## Default

tap_flag = 1

(Leven1) I. Leven, I. Azuri, L. Kronik and O. Hod, J. Chem. Phys. 140, 104106 (2014).

(Leven2) I. Leven et al, J. Chem.Theory Comput. 12, 2896-905 (2016).

(Maaravi) T. Maaravi et al, J. Phys. Chem. C 121, 22826-22835 (2017).