# bond_style harmonic/shift/cut/omp command

## Syntax

bond_style harmonic/shift/cut

## Examples

bond_style harmonic/shift/cut
bond_coeff 5 10.0 0.5 1.0

## Description

The harmonic/shift/cut bond style is a shifted harmonic bond that uses the potential

$E = \frac{U_{\text{min}}}{(r_0-r_c)^2} \left[ (r-r_0)^2-(r_c-r_0)^2 \right]$

where $$r_0$$ is the equilibrium bond distance, and rc the critical distance. The bond potential is zero for distances $$r > r_c$$. The potential is $$-U_{\text{min}}$$ at $$r_0$$ and zero at $$r_c$$. The spring constant is $$k = U_{\text{min}} / [ 2 (r_0-r_c)^2]$$.

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:

• $$U_{\text{min}}$$ (energy)

• $$r_0$$ (distance)

• $$r_c$$ (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 Speed packages doc 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, USER-INTEL, KOKKOS, USER-OMP and OPT packages, respectively. They are only enabled if LAMMPS was built with those packages. See the Build package doc 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 Speed packages doc 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 USER-MISC package. See the Build package doc page for more info.