Talk:Lonsdaleite

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Untitled[edit]

How can it be diamond if it does not have the same lattice structure as diamond ? ----FvdP 19:34 12 Jun 2003 (UTC)

A hardness of 3? On what scale? --Carnildo 18:09, 26 Aug 2004 (UTC)

Name[edit]

Is this named after anyone? —Preceding unsigned comment added by 134.250.72.121 (talkcontribs)

Arrgh?![edit]

"This ring structure is the most stable conformation of cyclohexane, and this contributes to the stability of diamond, which is the most stable allotrope of carbon. This stability is responsible for diamond's extreme hardness."

This is utter nonsense, yes the chair is the most stable conformation of cyclohexane, but diamond IS NOT the most stable allotrope of carbon, this is only the case at high pressure. At standard temperature and pressure, the mast stable allotrope is graphite (due to the greater phonon free energy, if you're interested). Also, hardness is not determined by energetic stability, it is determined by the stiffness (Rockwell hardness) or resistance to plastic flow (vickers hardness or Mohs scale). Will edit these bits.

Arrgh?! version 2[edit]

After more reading, the whole lattice structure section consists of masses of awful science, and basically needs to be deleted and rewritten. —The preceding unsigned comment was added by 131.111.195.8 (talk) 16:30, August 20, 2007 (UTC)

What Hardness is it[edit]

I found value for hardness of 3 Mohs as well as 7-8 in different referencess. Lonsdaleite structure is similar to graphite hP4 in Pearson symbolizm. So I more belive it is 3.

Why is this called "diamond" ???[edit]

It would be enlightening if the article included an explanation of why Lonsdaleite is termed a form of diamond.

Not a chemist, I don't know the answer myself. But why would one arrangement of carbon molecules be given the same name as a different one?Daqu (talk) 21:25, 1 January 2009 (UTC)

I believe lonsdaleite is a form of diamond. Just from what I have read from this article, it would appear to be so. Similar structure and hardness would cause one to think it is a type of diamond. Whether it is diamond or not, try to get in contact with a chemist.

A diamond, by definition, has a cubic arrangement of atoms. This most assuredly does not; it is hexagonal. It should simply be called by its name, Lonsdaleite, and be referred to as an allotrope of carbon. JohndanR (talk) 21:06, 12 December 2016 (UTC)

Harder than Diamond by 58% ?[edit]

I found this on Newscientist, which actually linked here. I think that perhaps this article should be revised to mention this. Link: http://www.newscientist.com/article/dn16610-diamond-no-longer-natures-hardest-material.html —Preceding unsigned comment added by 86.152.4.78 (talk) 19:25, 16 February 2009 (UTC)

Another comment: In the sentence (in the "== Properties ==" section), that starts out "Lonsdaleite is simulated to be 58% harder than diamond", the word "simulated" does not seem right. Shouldn't it say "estimated" instead? Even if some mathematical model -- (such as a "simulation"!) -- were to be used to do the estimating, IMHO it is still estimating -- (right?) (any comments? or advice? Thanks!..) --Mike Schwartz (talk) 17:58, 15 February 2011 (UTC)
Not really: it is a theoretical calculation ("computer simulation" if you wish), but it is accurate within its assumptions. Materialscientist (talk) 00:14, 16 February 2011 (UTC)
Semantically, 'simulated to be... X' is poor English. Scientifically, these sorts of simulations are worked up from extremely reliable first principles and tend, like simulating the trajectory of a shell in vacuo, to be accurate. It is not like predicting weather or climate. JohndanR (talk) 21:14, 12 December 2016 (UTC)

--- "It is accurate.." is utter rubbish. Until it has been experimentally verified, it is simply a model derived calculation. To claim a estimate as the fact is to confuse an observation with a calculation. Until someone can cite a reference that actually measured the hardness 58% greater than diamond (cubic) it should not be stated as fact. Period. I am changing.71.31.149.105 (talk) 13:32, 4 May 2012 (UTC)

Reported from the Tunguska impact site[edit]

Section Occurrence: "It has also been reported from the Tunguska impact site." I think a reference should be added here or else the sentence deleted. I could not find any information of such found and Tunguska itself is quite a contraversial topic. (Danapit (talk) 12:19, 29 November 2012 (UTC))

part of the article is ripped verbatim from a book[edit]

"The Mohs hardness of diamond is 10, and the lower hardness of lonsdaleite is chiefly attributed to impurities and imperfections in the naturally occurring material. A simulated pure sample has been calculated to be 58% harder than diamond" This paragraph is copied verbatim from page 636 in the book Computational Methods and Experimental Measurements XV, by G. M. Carlomagno & C. A. Brebbia, WIT Press, 2011, ISBN 978-1-84564-540-3 . By verbatim I mean not even rephrased nor using synonyms, verbatim as per definition. This part will be removed by me and rewritten, but ultimately should be entirely rewritten with new refs as the book "computational methods and experimental meassurements XV" cites the exact same refs as the former wikipedia refs (mindat. org and the book about w-BN and lonsdaleite) : a "serious" book citing mindat.org as a ref is a joke. The inline refs can be seen in the actual book (which I happen to have read) in the ref page (644) at the end of the chapter , but not on books.google.com as the poage 644 preview is unavailable, still here is the google book link for means of comparing (page 636 -which is available- with the former wiki paragraph) : http://books.google.fr/books?id=QjGO_-72oksC&printsec=frontcover&hl=fr#v=onepage&q&f=false — Preceding unsigned comment added by 82.240.163.245 (talk) 02:43, 2 January 2014 (UTC)

Nothing About This Article Is Correct[edit]

Obviously this article needs an entire rewrite considering it is now suspected that lonsdaleite as describe does not even exist. However, I will not be the one rewriting it. CosmicLifeform (talk) 17:40, 2 December 2014 (UTC)

See also: Wurtzite structure and iceane / comparison to cubic diamond[edit]

Currently, the article about wurtzite crystal structure contains a reference to this carbon allotrope while pointing out the structural similarties to lonsdaleite. However, in this article the term 'wurtzite' is not even mentioned once. Although the latter refers to binary compounds, it would be helpful for readers with less prior knowlegde of these matters.

Moreover, a cross-reference to the compound iceane and vice-versa, which seems to be related to lonsdaleite in the same manner as adamantane to cubic diamond (although not stated here, I would be glad if someone can cofirm this), could be included as well.

Considering the confusion some readers express in the comments section, adding a comparison between cubic and hexagonal diamond regarding chemical bondage might also seem necessary, such as the difference in rotational angles of the carbon atoms, which amounts to approximately 60° for all bonds in 'usual' cubic diamond. Lonsdaleite, however, exhibits bonds (the vertical ones in the image illustrating the crystal structure) without such a rotation. This property accounts for the hexagonal crystal structure and the lack of centrosymmetry.

To answer the question why lonsdaleite should be considered a type of diamond, it can be said that both crystallic allotropes of carbon with regular three-dimensional structure exhibit very similar physical properties such great hardness and transparacy in contrast to the more stable graphite, which the former compounds can be synthesized from under conditions of extremely high pressure and temperature - the hexagonal one through impact in a short amount of time, the other one through long-time exposure. (These are my findings from what I have read, again, I would be glad if someone can confirm this.) — Preceding unsigned comment added by 212.197.171.130 (talk) 17:52, 8 June 2016 (UTC)