\(\renewcommand{\AA}{\text{Å}}\)

# bond_style mesocnt command

## Syntax

    bond_style mesocnt

## Examples

    bond_style mesocnt
    bond_coeff 1 C 10 10 20.0
    bond_coeff 4 custom 800.0 10.0

## Description

Added in version 15Sep2022.

The mesocnt bond style is a wrapper for the harmonic style, and uses the potential

\[E = K (r - r_0)^2\]

where \(r_0\) is the equilibrium bond distance. Note that the usual 1/2 factor is included in \(K\). The style implements parameterization presets of \(K\) for mesoscopic simulations of carbon nanotubes based on the atomistic simulations of (Srivastava).

Other presets can be readily implemented in the future.

The following coefficients must be defined for each bond type via the bond_coeff command as in the example above, or in the data file or restart files read by the read_data or read_restart commands:

- preset = C or custom

- additional parameters depending on preset

Preset C is for carbon nanotubes, and the additional parameters are:

- chiral index \(n\) (unitless)

- chiral index \(m\) (unitless)

- \(r_0\) (distance)

Preset custom is simply a direct wrapper for the harmonic style, and the additional parameters are:

- \(K\) (energy/distance^2)

- \(r_0\) (distance)

## Restrictions

This bond style can only be used if LAMMPS was built with the MOLECULE and MESONT packages. See the Build package page for more info.

## Related commands

bond_coeff, delete_bonds

## Default

none

(Srivastava) Zhigilei, Wei and Srivastava, Phys. Rev. B 71, 165417 (2005).