\(\renewcommand{\AA}{\text{Å}}\)

# bond_style nonlinear command

Accelerator Variants: nonlinear/omp

## Syntax

    bond_style nonlinear

## Examples

    bond_style nonlinear
    bond_coeff 2 100.0 1.1 1.4

## Description

The nonlinear bond style uses the potential

\[E = \frac{\epsilon (r - r_0)^2}{ [ \lambda^2 - (r - r_0)^2 ]}\]

to define an anharmonic spring (Rector) of equilibrium length \(r_0\) and maximum extension lamda.

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:

- \(\epsilon\) (energy)

- \(r_0\) (distance)

- \(\lambda\) (distance)

Styles with a gpu, intel, kk, omp, or opt suffix are functionally the same as the corresponding style without the suffix. They have been optimized to run faster, depending on your available hardware, as discussed on the Accelerator packages page. The accelerated styles take the same arguments and should produce the same results, except for round-off and precision issues.

These accelerated styles are part of the GPU, INTEL, KOKKOS, OPENMP, and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the Build package page for more info.

You can specify the accelerated styles explicitly in your input script by including their suffix, or you can use the -suffix command-line switch when you invoke LAMMPS, or you can use the suffix command in your input script.

See the Accelerator packages page for more instructions on how to use the accelerated styles effectively.

## Restrictions

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

## Related commands

bond_coeff, delete_bonds

## Default

none

(Rector) Rector, Van Swol, Henderson, Molecular Physics, 82, 1009 (1994).