Why is graph unstable

From graphite to graph

Carbon is by far the most versatile chemical element, and one of the most important for humans: Practically all vital biomolecules are based on a basic structure of carbon atoms - an innumerable number of different organic compounds.

Just as fascinating are the many different manifestations of elemental carbon: on the one hand a sparkling diamond, on the other hand black coal. Carbon fibers are now widely used as a lightweight material, from fishing rods to bicycle frames to aircraft parts. There are also the exotic-looking carbon nanotubes and the football-like fullerenes with their very own physical and chemical properties.

Exotic carbon in the pencil line

Graphene, one of those exotic species, is actually not all that exotic: even the smallest amounts appear in every pencil stroke. The lead in the pencil is made of graphite. This form of carbon consists of innumerable layers. In each of these layers, in turn, the carbon atoms, arranged in hexagons, form an absolutely regular lattice. This layer structure already gives graphite interesting properties: For example, it conducts electricity excellently - but only parallel to the course of the layer, not across it.

A stack of three million of these layers forms just one millimeter of graphite. Scientists were already speculating over 70 years ago about how a single layer of graphite might behave. They gave the - at the time still hypothetical - material the name graph. Such individual layers were already known from other carbon nanomaterials: In the nanotubes and fullerenes, they are formed into rolls and balls. These also have the characteristic hexagon pattern.

Nevertheless, no one assumed that graphene could actually exist as a free layer, in a sense a super-thin carbon film: a single layer of atoms simply had to be far too unstable, according to the widespread assumption.

Ansgar Kretschmer
Status: May 16, 2014

May 16, 2014