A model of 20 oranges is compared with the theoretical and experimental structure [credit: KU Leuven]
Peculiar? Maybe, but the clusters are just based on the triangular number sequence: 0,1,3,6,10 etc. (add one more than last time).
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Freestanding clusters of twenty gold atoms take the shape of a pyramid, researchers discovered.
This is in contrast with most elements, which organize themselves by forming shells around one central atom, says EurekAlert.
The team of researchers led by KU Leuven published their findings in Science Advances.
Clusters composed of a few atoms tend to be spherical. They are usually organized in shells of atoms around a central atom. This is the case for many elements, but not for gold!
Experiments and advanced computations have shown that freestanding clusters of twenty gold atoms take on a pyramidal shape.
Credit: Wikipedia
They have a triangular ground plane made up of ten neatly arranged atoms, with additional triangles of six and three atoms, topped by a single atom [see figure where a model of twenty oranges is compared with the theoretical and experimental structure].
The remarkable tetrahedral structure has now been imaged for the first time with a scanning tunnelling microscope. This high-tech microscope can visualise single atoms.
It operates at extremely low temperatures (269 degrees below zero) and uses quantum tunnelling of an electrical current from a sharp scanning metallic tip through the cluster and into the support. Quantum tunnelling is a process where electrical current flows between two conductors without any physical contact between them.
Full article here.
via Tallbloke’s Talkshop
January 6, 2020 at 04:16AM
Iowa Climate Science Education 