Talk:Graphene
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From the article:
"It is not an allotrope of carbon because the sheet is of finite size and other elements appear at the edge"
For that matter, the same occurs for diamond and graphite. Diamond is merely a matrix of carbon atoms bonded in a tetrahedral shape. Graphite is series of benzene rings. In both allotropes, each carbon atom has a total of four bonds, assuming that the matrix is unbounded (in graphite, there are two single bonds and one double bond per atom). When the matrix ends, the carbon atoms typically bond to hydrogen atoms at their surface to terminate the extra loose bonds. And yet, the two are still considered allotropes.
It is not, then, for this reason that graphene is not a new allotrope.
From my reading, graphene is similar to graphite in that it is a single layer of a graphite matrix. See here (IUPAC). Note that graphene is a singular sheet of graphite, just as goose is the singular of geese. For this reason, graphene is not an allotrope, because graphene and graphite are the same.
Also, note that graphite is a 'quasi-infinite' matrix.
Graphene is chemically and structurally quite different from graphite. For example, it is a semi-conductor and it is prevented from melting by micrometer-scale random corrugations. Whether it is different enough to be an allotrope is tricky, but I'd say it is. I completely agree that the finiteness of graphene is irrelevant and should not be mentioned. Even other allotropes of carbon are finite in some or all dimensions, including nanotubes and buckyballs. --Alistair
Is graphene really a 2D crystal???, graphene is not , strictly speaking, a crystal in the full sense of the word, since I don't think you can speak of "translational symmetry" because that would mean you could consider its dimentions to be much , much larger than the unit cell , which is definitely not the case for graphene. --85.138.18.55 18:07, 12 April 2006 (UTC) Pedro
It certainly makes sense to say graphene is a 2D crystal - it has two distinct translation symmetries. Similarly, a carbon nanotube is a 1D crystal. --Alistair
In the section on electron transport, it might be more accurate to say that the "charge carriers" obey a Dirac equation, not the electrons. That way, the statement includes holes too, but excludes non-conduction electrons. However, this should be checked with somebody who actually knows about the electronic structure! --Alistair
I would second the amendment of "electrons" to "charge carriers": this is the terminology used in Novoselov et al. Science 306 2004. The discussion of whether or not graphene is an allotrope of carbon is flawed (the 'thickness' of a material is irrelevant, an allotrope is a structurally different form of the same element) and boils down to semantics in the end; more importantly I don't believe that this is the best way to start what is supposed to be an informative article. When we give talks we normally start with the dimensionality aspects: i.e. 0D = quantum dots, atoms etc., 1D = nanowires, nanotubes, 3D = diamond, graphite etc., and now 2D = monolayer graphene, monolayer hexagonal boron nitride etc. which places the discovery in context (note that dimensionality in this sense refers to electronic transport properties and not the structure itself). Graphene is not just a singular noun, Kris, and graphene and graphite are most definitely not the same - they differ in terms of band structure (graphene is a zero-gap semimetal), transport properties (ballistic conduction at room temperature in graphene), crystal structure (graphite has a c unit cell parameter) etc. The discussion of defects is interesting, but again not necessarily the best way to start the article in my opinion. - T. Booth Mbcx0tjb 13:19, 24 March 2007 (UTC)
