Abuzz about uranium

A type of atomic vibration never before seen in ordinary solid materials has been observed in uranium.

HEAVY VIBES. X rays pinpointed never-before-observed atomic vibrations in this ultrapure uranium crystal. C. Opeil/Los Alamos National Lab

Using X rays and neutrons to monitor crystals of the heavy metal while they’re being heated in a furnace, Michael E. Manley of Los Alamos (N.M.) National Laboratory and his colleagues have detected vibrations long-predicted to randomly occur in solids within isolated groups of two or three atoms.

The solitary crystal vibrations, dubbed lattice solitons, appeared at temperatures of 177°C and higher. They probably occur in many solids but are harder to detect in them than in uranium, Manley says. He and his colleagues report their findings in the March 31 Physical Review Letters.

Other common atomic vibrations associated with heating spread easily throughout a material. But because the newfound vibrations have an unusually large amplitude and a frequency uncommon for uranium, they don’t spread to surrounding atoms.

The solitary vibrations mimic structural defects that affect crystal malleability, Manley says. So, the new findings may account for a long-known, but unexplained drop in uranium pliability at 177°C.

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