The interactive animation to the right depicts the structure of diamond.
Diamond adopts a cubic lattice, but if you rotate the structure (run your mouse over it) so that one of the corners of the cube points upward, you should be able to see the tetrahedral relationship between closest neighbour carbon atoms quite clearly (I’ve re-drawn this below the animation so you know what to look for).
The semiconductors silicon and germanium adopt the same structure – but we are used to thinking of these as solid state structures rather than an over-bonded organic molecule, so the model is less of a surprise.
The side of the cube above is approximately 0.357nm and the space group is Fd3m(Oh7) (Space Groups for Solid State Scientists 2nd Edition, Burns and Glazer, Academic Press 1990, p152-4)
The structure is built in Flash using our molecular modeller (previous post); it was derived from a larger 3D diamond structure built for an update to What is Nanotechnology? for the Nanofolio MSc courses.
The new project calls for dynamic atoms within the structure, which we will use to explore the differences between matter in bulk (diamond) and ‘soft matter’, that is the basis of most molecular nanotechnology.
As a first stage towards this you might have noticed here that the atoms gently fade in when the structure first loads – the final animation has atoms appearing, disappearing and changing their nature on command – but more about that in a future post…