Michael, with BurrMan's kind example in front of me I managed to throw together a lattice in short order. The main "aha!" moment was when I was having difficult aligning the atoms with the "sticks"; I realised that using sticks sharpened like pencils at both ends (i.e. with cones on them) would allow me to place spheres very accurately at the intersection of the sticks. Once that was in place I simply used copy and snap and it made everything very easy. I'd even go as far as to say it was actually fun.

While the on-screen representation is OK, I think I need to play with the lights and other options further as my screenshot is not as pretty as the one BurrMan uploaded. Either that or keep looking for renderers - the thread to which you referred me was useful.

I have a question: the lattice is simple but there are many elements: 90 sticks and 60 atoms per lattice and I have two lattices plus in addition another couple of hundred atoms hanging around between lattices, a product of the array tool. This slows the PC down a little. Can I do anything to speed things up? For example, if I do a boolean union on the sticks (which presumably just touch each other at their points) and the atoms in the lattice, would that make life easier for MoI?

Thanks
Dan