Re: [Jmol-users] crystal cell terminology

[Miguel H. <mt...@mt...>]

> By *definition* the unit cell is the smallest repeat unit for the choice
> of symmetry. So there is no need for "singleton" anything, the unit cell
> is the unit cell.

Hmmm ... I'm not sure I agree ... let me try to explain.


Sometimes, you see a 'unit cell' by itself. Sometimes, you see a
collection of 'unit cells'. When you see a collection, each one of those
things is a 'unit cell'.

In a context of a discussion (and in the context of programming), there
are times when you need to distinguish between these two cases.

For example:
  In a collection of unit cells each of the individual unit cells is a
copy of THE unit cell.

In the real world they are all all equal. But in the programming world,
one of them is *more equal* than all the others.

I need to give that one a special name.

I think that I need three names which have unambiguous meaning.

  unit cell -> any unit cell
  THE unit cell -> the one which has special meaning because it
                   is the parent of all the other clones
  collection of unit cells -> see below


> Supercell smacks of sub- and supergroup relations between spacegroups,
> and this has pretty well defined meanings already, so that nomenclature
> wouldn't be my first choice.

Good. If this is a conflict then we will avoid it.

> Multi_cell? Cell packing?

I could go for multicell

Jan proposed 'crystal' ... What do you think of that?


Miguel