Knowledge Bank

Small clusters of tin, titanium, chromium, iron, and nickel do not adopt bulk structures, according to molecular orbital calculations. Reasons are discussed. On the other hand, theory is capable of producing structures for large molecules in molecular crystals. Structures calculated and determined by X-ray diffraction for diiron hexacarbony1 acetylenes are analyzed. However, the packing structure of molecules in molecular crystals may, as for the atoms, not be generally reproducible from considerations of just a few units.