Sorted neighbor list

[pastewka]

The neighbor list is currently sorted by first index only, it may be beneficial for some applications to have a fully sorted neighbor list. This would make neighbor list construction slower, but only slightly so. Any opinions on this?

[jameskermode]

Maybe optional and defaulting to not sorting?

[griessej]

I agree with James. If this is needed, it should be passed explicitly by keyword. Applications that do not need this will not suffer any performance loss.

[pastewka]

That would be an option. I'll look into this.