Utility function for finding shells
Description
As a user the first thing you need to do when trying out hiphive for your system is to find the shells of your systems. From the shells (and our slick estimate_maximum_cutoff function) you can then determine suitable cutoffs.
I suggest we introduce a utility function for finding shells to make life easier for our users (and ourselves).
Task
- use ASE's neighbor list functionality to generate a list of pair distances
- bin the list by distance and type (as requested by the user)
Edited by Paul Erhart