Credit: ACS

Small atomic cages are all the rage. Those made of carbon – better known as fullerenes – are the most common, but other elements in the periodic table are now catching up. The latest addition to the family is the world’s tiniest tin can – a hollow cage made from 12 atoms that may be able to accommodate another atom at its core.

While investigating small tin (Sn) and germanium clusters, Lai-Sheng Wang and co-workers at Washington State University, Pacific Northwest National Laboratory and Utah State University found that, unlike all the others, Sn12– gave rise to a simple and well-resolved photoelectron spectrum. This observation implied a highly symmetric structure and comparison with density functional theory calculations suggested that a slightly distorted icosahedron – a polyhedron with 20 triangular faces – is the most likely candidate.

Adding another electron to this cluster gives Sn122–, which adopts an almost ideal icosahedral structure and has a diameter of just over 6 Å. It should be possible to synthesize Sn122– in the solid state because calculations show that it is stable. The encapsulation of a cadmium atom inside this cage to form a ‘superatom’ has already been studied theoretically and is one of many potential endohedral clusters awaiting discovery.

Earlier this year Wang and co-workers reported that clusters containing 16, 17 or 18 gold atoms also formed cages.