Talk:Cubic crystal system

Simple Cubic

Simple Cubic isn't the proper name of the crystal system. According to the International tables of crystallography, It's Primitive Cubic. Simple cubic is a colloquialism with some unknown etymology. — Preceding unsigned comment added by 128.111.185.93 (talk) 20:18, 9 February 2012 (UTC)

Books using "Simple cubic": [1].

Books using "Primitive cubic": [2]

International Tables of Crystallography pages using "Simple cubic": [3]

International Tables of Crystallography pages using "Primitive cubic": [4]

In both cases it seems that both are acceptable but "simple" is a bit more common than "primitive". In the article I suggest to write "simple cubic (also called primitive cubic)". OK? --Steve (talk) 20:35, 9 February 2012 (UTC)

I would agree but the word simple isn't a descriptor in the official tables e.g. from volume A:[5]

The wiki article on Bravais lattices gets this correct and describes the primitive cubic lattice as primitive and doesn't use simple as a descriptor for any of the lattices. The use of simple cubic has no official designation even though people continually insist on using it because it came into use prior to the adoption of the tables. I'd be satisfied though with writing "primitive cubic (also called simple cubic)" — Preceding unsigned comment added by 128.111.185.93 (talk) 01:09, 10 February 2012 (UTC)

This is not part of "the official tables"?? Hmm, actually, there is no need to argue about this. I'm happy enough with your compromise suggestion, where we write "primitive cubic (also called simple cubic)" at the beginning of the article and just plain "primitive cubic" later on in the article. I'll go ahead and do that if you don't do it first! :-) --Steve (talk) 21:34, 10 February 2012 (UTC)

The tables have multiple authors and the editors aren't all necessarily dogmatic. More importantly, the article doesn't come from either volumes A or A1 in tables, which specifically specify all relevant definitions. The link I provided is in reference to the official listing of the 14 Bravais lattices. The reference also includes the Pearson symbol of all the lattices which should be used for the description of the lattice. Instead of merely P, F, and I, it should be cP, cF, and cI. The German article on the cubic system takes care to establish the right Pearson symbols. — Preceding unsigned comment added by 128.111.185.93 (talk) 02:58, 11 February 2012 (UTC)

That makes sense--I see why we should treat Volume A as more authoritative than Volume D about what the lattices are named. While you're here, if you see other errors or omissions in the article I hope you feel free to fix them! :-) --Steve (talk) 13:36, 11 February 2012 (UTC)

Large changes

I've made some large changes to this article. Most important is that there seemed to be some confusion as to the difference between a cubic lattice and a cubic crystal. This article should be about the cubic lattice with the somewhat confusing name cubic crystal system. For example, the figures show lattice points not atoms, and the pure metal examples mentioned are crystals with a one-atom basis centered on each lattice point. I've also introduced a new table giving the cubic point and space groups. O. Prytz 17:26, 5 June 2006 (UTC)

• I made the table much larger and comprehensive, as the previous one was useless when trying to decipher the much superior German page and bring information over to the English version. 130.39.188.130 (talk) 22:21, 8 July 2009 (UTC)

Beginning to Change

I've begun to change the article. I'll write it on the level of a college freshman level texbook. I'll try to keep it as straightforward as possible. It's better to convey less information understandably than talk like a professor and have no one understand you. If they want complete information, they can go to the nearest college's library.

You assume they live near enough to a college with books in English. Not that I dissagree with keeping the article straightfoward but I see nothing wrong with linking to more in-depth articles. JIMp _talk·cont 13:43, 7 July 2009 (UTC)

Covalent Bonds?

The pictures of the FCC and BCC both contain som diagonal lines? That ins't right, is it? At least not if the lines are interpreted as covalent bonds...

The diagonals clarify the positions of the lattice points, regardless of covalent bonds.--Patrick 12:42, 13 January 2006 (UTC)

Writing Style/Level

This writing style of this article belongs in a scientific journal, not an encyclopedia. Having taken two semesters of chemistry - and thus having at least a vague idea of lattice structures - was no help to me in trying to decipher this technically-written article. Perhaps a summary or clarification of the article would help us less educated folk understand it. Thanks

I agree ;).

I agree too. :)

Not bad, but could do with some more information on the various crystal structures eg. volumes of the interstitial sites in each lattice, examples of materials with each lattice (eg. fcc copper, bcc iron), a reference to the hexagonal packing system from fcc (which is not really intuitive!) ..and perhaps some explanation/avoidance of more "technical" terms eg."Galenal type" - not everybody needs passing references to complicated concepts. Could be good - you obviously know your stuff!

-- I'm terrible at writing stuff in wiki format, so here's some info that was being asked about above (figured I'd post it after just having to rederive this stuff for a solution set I'm making). FCC: 8 tetrahedral sites. Size: 0.414r_a FCC: 4 octahedral sites. Size: 0.225r_a BCC: 12 tetrahedral sites. Size: 0.291r_a BCC: 6 octahedral sites. Size: 0.154r_a Where r_a is the radius of the "A" atom on the actual lattice sites of the crystal. — Preceding unsigned comment added by 131.215.30.166 (talk) 21:44, 30 November 2011 (UTC)

Gyroidal class

Article says that cuprite belongs into gyroidal class but webmineral.com puts it into hexoctahedral class. Siim 18:48, 5 February 2006 (UTC)

Agreed. Fixed. My reference (added) Klein & Hurlbut states that cuprite was long considered gyroidal, but was eliminated leaving no known mineral example. Vsmith 19:38, 5 February 2006 (UTC)

petzite is supposed to be gyroidal - added it. Geologyguy 16:58, 22 April 2006 (UTC)

Polonium as simple cubic reference?

I read in a paper that J Chem Phys 14:569 proves that Po crystallizes in a simple cubic form, but I'm too lazy to check it out at the library. Anybody wanna help out and look it up?

Not right now. Maybe later. Is that J. Chem. Phys. A, B, or C? Crystal whacker (talk) 03:00, 20 November 2008 (UTC)

I put the direct web link into the article. In 1946, there was just one J. Chem Phys. (Ah, simpler times.) --Steve (talk) 07:12, 20 November 2008 (UTC)

Coordination number of zincblende

I don't remember offhand what the coordination number is for zincblende atoms. I added that info for NaCl and CsCl type structures. Crystal whacker (talk) 03:01, 20 November 2008 (UTC)

Each atom of type A has four nearest neighbors, all type B, in a tetrahedral configuration.

If the lattice constant is a, then the Bravais lattice vectors are (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2). There's an A at the origin, and a B at (a/4,a/4,a/4). The four nearest neighbors of the A at the origin are the B's at (a/4,a/4,a/4), (-a/4,-a/4,a/4), (-a/4,a/4,-a/4), (a/4,-a/4,-a/4). And these do indeed form a tetrahedron.

So the answer is 4. --Steve (talk) 07:12, 20 November 2008 (UTC)

Tetartoidal vs. Tetratoidal

I've found Tetartoidal when translating this article to my catalan language and bein in a "cubic" environement I've thought by a common sense deduction it should be Tetratoidal, but maybe I have opened a pandora box

Here are the google books results

• Tetartoidal
• Tetratoidal

Cheers--Mcapdevila (talk) 05:40, 16 July 2011 (UTC)

Tetartoidal is correct, see tetartoidal class on Webmineral. Vsmith (talk) 16:06, 16 July 2011 (UTC)

There are 8 google book results for tetratoidal (only 4 of which are in English). There are hundreds of results for tetartoidal. Therefore I think we have to assume that 4 people misspelled the word in their books, and tetartoidal is correct. :-) --Steve (talk) 22:23, 16 July 2011 (UTC)

The term comes from Ancient Greek τέταρτος (tetartos), meaning "fourth" (as an ordinal) or "quarter" (one fourth), + the suffix -oid(al).  --Lambiam 01:16, 21 October 2012 (UTC)

Grammar

The grammar has broken down in the tenth line.

The first sentence under the heading "Crystal classes" is also ungrammatical.

I would not say it is ungrammatical, but the phrases in the first sentence are not in the same order as the columns in the box nearby, if the columns are read from left to right.

The sentence "The no of second nearest neighbours are 6.third nearest neighbours are 24." has a little grammatical error. The "no" should be "No."

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Description of rocksalt structure as interpenetrating lattices

I believe this is a fundamental misunderstanding of the differences between a crystal system and a lattice. The lattice is the array of infinitesimal points in space. The crystal system is the way in which the motif(s) decorate this lattice. The rocksalt structure is not two interpenetrating face-centred cubic lattices. There is one lattice with two interpenetrating nets of face centred cubic systems of Na+ and Cl-

This misunderstanding is laid out in Appx. 12 of Burns and Glazer if anyone wants to look at it.

Sgssmlpl (talk) 02:53, 6 May 2019 (UTC)

Engineering relevance of BCC and FCC

This article only about the crystal system on a mostly mathematical and crystallographic level. However, the mechanical properties BCC and FCC are hugely important for steelmaking and metallurgy in general. Information on these structures (e.g. slip planes, martensite-austenite transformation, prevalence of FCC and BCC in engineering materials, importance of symmetry, etc.) really needs to be on wikipedia, but I'm not sure if it should be for example a subsection on this page or a separate page. Yellowy cake (talk) 18:33, 14 August 2019 (UTC)

Good point! I suggest that either

• a separate, linked article, titled "Cubic crystal system (engineering)" or
• a new major section of this page, titled "In engineering"

would be an appropriate place for this kind of information. However, we should also consider whether a more general article on the relevance of all crystal classes - not just cubic - in engineering is warranted, which we might call "Crystal class (engineering)". yoyo (talk) 00:48, 27 August 2019 (UTC)

Notation systems for crystal classes

Alternative A: Explain more

The section § Crystal classes begins with the following:

The isometric crystal system class names, point groups (in Schönflies notation, Hermann–Mauguin notation, orbifold, and Coxeter notation), type, examples, International Tables for Crystallography space group number,[2] and space groups are listed in the table below.

Before this complex sentence, I think it would be good to

1. state that each crystal class has a name, identical to that of its (crystallographic) point group;
2. state that there are several "Notation systems for crystal classes";
3. state that crystal class notation systems include Schönflies notation, Hermann–Mauguin notation, orbifold notation, Coxeter notation and that of Conway;
4. give the appropriate wikilinks for each notation system, just once, here;
5. remove duplicate wikilinks to these notation systems from later in the article;
6. state (if known!) the fields that commonly use each notation system.

This information would give a better introduction to the welter of information in the table. Perhaps it should be a separate, introductory section "Notation systems for crystal classes". Or maybe an article of its own, which could be linked here in the intro to the table. In this direction, note that

1. the (start-class) article crystallographic point group contains a basic discussion of three notation systems, their correspondences and their users, but little else;
2. the (C-class) article crystal system also invokes the different notation systems, without describing or comparing them;
3. and even the (B-class) article crystal structure uses the different notation systems, without describing or comparing them.

Perhaps the first of these three, (crystallographic point group), is the best place to offer a fuller description and discussion of the various notation systems?

Alternative B: Say less

An alternative: reduce the amount of information in this table, making it simpler to understand. For a first reading, nobody will need all the information given in this section. We could, for example, entirely remove any reference to the orbifold or Coxeter notations. (Though somebody would protest, most likely.)

Class number is unclear

Note that the "International Tables for Crystallography" space group numbers given in the first column of the table each corresponds to exactly one of the space group codes ("names") given in the last three columns; however the table doesn't make clear which one. Consider combining the number and its corresponding code in the last three columns e.g. "195: P23" in the first cell of column "Primitive". yoyo (talk) 05:20, 27 August 2019 (UTC)

Yes, this section is completely unclear. The relationship to cubic crystal systems is not given. Geoffrey.landis (talk) 22:12, 11 February 2022 (UTC)

unclear

The phrase

These tetrahedral voids are not local maxima and are not technically voids, but they do occasionally appear in multi-atom unit cells.

is unclear because it is not stated what should be maximum in them nor what the word technically exactly means. This statement for the bcc holds for the following fcc? Does "appear" mean "contain atoms"?

It is possible to give the relative radii of the octahedral and tetrahedral holes? This is interesting because the article steel says that the fcc structure is "more open" than the bcc, in spite of its higher packing factor (this is why I arrived here).

pietro151.29.1.146 (talk) 13:01, 24 January 2020 (UTC)

The octahedral holes of the bcc are regular as I always supposed (the symmetry is cubic/isotropic)? The o-hole at at middle of a face is at side/sqr(2) from the four neighbor at the corners of its face and at side/2 from the two on the axis of the face. If I have mistaken this calculation, please tell me and accept my apologies. If not, the distortion seems to me important enough to be stated. And must be followed by an explicit statement of the regular/irregular nature of all the holes, because otherwise the reader is left with doubts.

A minor point that hampers the section is that in bcc/fcc the holes are listed in reverse order.

I'd like to second the 'unclear', but from a different perspective. I do not possess any familiarity with these terms. I could not identify an octahedral hole from a tetrahedral hole (or any other types). If this required a link to a crystallography page, I'd find that useful. However, as a novice, this entire section is unclear. Could it be written for non-crystallographers or is it just too difficult to do that? Petedskier (talk) 17:25, 20 December 2021 (UTC)