Talk:Rhombohedral crystal system
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My reference book (a Peterson field guide) lists the same name for the 3 and 3bar classes, which I think must be a typo. But I put it in anyway, rather than just take a guess based on the names of the triclinic classes, as I did at first. If anyone knows better, please fix it. Tantalate 19:46, 21 May 2004 (UTC)
[edit] Name change?
I would like to rename this and other articles so that all of the articles describing the seven crystal systems are named the same way. For example, I would like to rename this article Rombohedral crystal system. That way it woun't be confued with the general geometric shape. Any objections? O. Prytz 17:39, 5 June 2006 (UTC)
- See my response at Talk:Orthorhombic, ditto for here. Vsmith 00:03, 6 June 2006 (UTC)
[edit] Oversight
The question as to merging the trigonal system in with hexagonal system is one perpetual confusing question in crystallography. Some people certainly class the trigonal system as a kind of subset of the hexagonal.
However, at the moment, there is an omission in the coverage of the crystal systems: within the trigonal system there are both primitive (P-centered) and rhombohedral (R-centered) lattices. At the moment a search for "trigonal" redirects you to "rhombohedral". This latter entry has the statement 'There exists only one rhombohedral Bravais lattice.' True, but there is a primitive trigonal Bravais lattice, from which many space groups like P3 exist. These are not mentioned at all (so far as I can see) in the current coverage on crystal systems. In reality rhombohedral lattices are one component of the trigonal system, which consists of P- and R-centered lattices. (See for example http://cst-www.nrl.navy.mil/lattice/spcgrp/trigonal.html). The French entry on crystal systems would be good to translate and merge here (http://fr.wikipedia.org/wiki/Système_cristallin#Classification_morphologique_:_les_syst.C3.A8mes_cristallins). The latter contains a note on the confusion "Trigonal versus rhomboédrique", although I am not sure it is totally correct either.Octopodes 04:50, 11 January 2007 (UTC)
