$$\renewcommand{\AA}{\text{Å}}$$

# compute contact/atom command¶

## Syntax¶

compute ID group-ID contact/atom group2-ID

• ID, group-ID are documented in compute command

• contact/atom = style name of this compute command

• group2-ID = optional argument to restrict which atoms to consider for contacts (see below)

## Examples¶

compute 1 all contact/atom
compute 1 all contact/atom mygroup


## Description¶

Define a computation that calculates the number of contacts for each atom in a group.

The contact number is defined for finite-size spherical particles as the number of neighbor atoms which overlap the central particle, meaning that their distance of separation is less than or equal to the sum of the radii of the two particles.

The value of the contact number will be 0.0 for atoms not in the specified compute group.

## Output info¶

This compute calculates a per-atom vector, whose values can be accessed by any command that uses per-atom values from a compute as input. See the Howto output page for an overview of LAMMPS output options.

The per-atom vector values will be a number $$\ge 0.0$$, as explained above.

The optional group2-ID argument allows to specify from which group atoms contribute to the coordination number. Default setting is group ‘all.’

## Restrictions¶

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

This compute requires that atoms store a radius as defined by the atom_style sphere command.

group2-ID = all

none