Riff-in-Thyme said:
Shattering records: Thinnest glass in Guinness book
At just a molecule thick, it’s a new record: The world’s thinnest sheet of glass, a serendipitous discovery by scientists at Cornell and Germany’s University of Ulm, is recorded for posterity in the Guinness Book of World Records.
The “pane” of glass, so impossibly thin that its individual silicon and oxygen atoms are clearly visible via electron microscopy, was identified in the lab of David A. Muller, professor of applied and engineering physics and director of the Kavli Institute at Cornell for Nanoscale Science.
I would have been prepared to swear that this was impossible, but stand corrected. Now thinking more clearly, there are two sheets of silicon atoms in perfect alignment. Each silicon atom is attached to four oxygen atoms and each oxygen atom to two silicon atoms. The oxygen atoms around the silicon atom want to form a tetrahedon (not a planar structure) and the angle between the two silicon atoms attached to the oxygen wants to be a tetrahedral angle. So the whole structure is five atoms thick, first layer of 3 oxygen, second layer of 2 silicon, central core of 2 oxygen, fourth layer of 2 silicon and final layer of 3 oxygen, giving a ratio of SiO2.
To get this to work as a 2-D structure as shown in the image, the bond angles of the central core of oxygen atoms would have to be heavily distorted away from the tetrahedral angle of 109.5 degrees towards 180 degrees. That would introduce a lot of strain into the structure, and this strain would help to explain why the layer of silicon atoms consists of irregular polygons rather than regular hexagons.