The authors of the 1968 study had suggested two possible crystal symmetries – space groups C2/m and C2/c. This, he points out, helps make theoretical calculations more reliable. Neutrons provide a higher contrast image than x-rays, because they can penetrate the copper container that houses the sample better.Īlthough Kraus and colleagues confirmed the 1968 study’s findings, including a higher and lower temperature polymorph, ‘the F–F distance is more accurate by about 70%’, Kraus says. While the 1960’s team diffracted x-rays off their sample, Kraus and colleagues used neutrons from a nuclear reactor.

Now, Kraus and his team have revisited fluorine’s solid structure. The researchers who recorded fluorine’s first – and until recently only – crystal structure in 1968 had to deal with several explosions as the solid halogen reacted with the copper sample holder. Or maybe it’s because it’s extremely reactive even at those temperatures. Maybe it’s because fluorine only crystallises at 54K (−219☌). ‘But the crystal structure of elemental fluorine has been determined only once, which rather surprised me.’ ‘There are, I think, about 80 or so crystal structure determinations for the various modifications of oxygen,’ he says. 2įluorine is one of the more widely used elements, so inorganic chemist Florian Kraus from Philipps-University Marburg assumed that its structure must have been studied at great length. In the process, a team of German chemists has managed to solve a controversy surrounding the frozen halogen’s crystal symmetry. The F1 atoms forming the cube are drawn yellow, the F2 atoms forming the octahedron are drawn in greenįifty years after fluorine’s crystal structure was first determined 1 – in experiments that involved explosions and midnight liquid helium handling – the element’s structure has finally been given a second look.

Atomic structure of fluorine