compute ID group-ID contact/atom
compute 1 all contact/atom
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.
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 Section_howto 15 for an overview of LAMMPS output options.
The per-atom vector values will be a number >= 0.0, as explained above.
This compute requires that atoms store a radius as defined by the atom_style sphere command.