pair_style none command
Using a pair style of none means pair forces and energies are not computed.
With this choice, the force cutoff is 0.0, which means that only atoms within the neighbor skin distance (see the neighbor command) are communicated between processors. You must insure the skin distance is large enough to acquire atoms needed for computing bonds, angles, etc.
A pair style of none will also prevent pairwise neighbor lists from being built. However if the neighbor style is bin, data structures for binning are still allocated. If the neighbor skin distance is small, then these data structures can consume a large amount of memory. So you should either set the neighbor style to nsq or set the skin distance to a larger value.
See the pair_style zero for a way to trigger the building of a neighbor lists, but compute no pairwise interactions.