Talk:Crystallographic point group

message: This is really a page of space groups.  They are an extension of point groups, which are normally for molecules. 220.244.224.8 05:19, 18 Feb 2005 (UTC)

message: Crystal class used to redirect to Crystal system. This was incorrect, so I changed it to redirect here, which I believe is more appropriate. Although there may be nuances here which I'm not certain about. Refs:
* http://ruby.colorado.edu/~smyth/G30102.html
* http://www.iucr.org/iucr-top/comm/cteach/pamphlets/22/node22.html
There seems to be better information on point groups on the Crystal system page? I dont know enough to fix the problem.. can someone who knows their stuff please fix it. 60.234.48.118 23:57, 14 March 2007 (UTC)
thread_title: Changed a redirect

message: This article was automatically assessed because at least one WikiProject had rated the article as start, and the rating on other projects was brought up to start class. BetacommandBot 09:46, 10 November 2007 (UTC)
thread_title:  WikiProject class rating

message: There is no explanation of the subscript 'd' placed after certain point groups of D, for example in D2d.   Also, under the discussion of possible subscripts for D, it mentions a possible v subscript, when that never seems to be used.  Am i right in thiking that 'd' basically takes the desciption given to 'v'. If so could someone who fully understands why 'd' is used instead of 'v' provide an explanation.  Thanks.  —Preceding unsigned comment added by 129.31.240.38 (talk) 14:49, 30 May 2010 (UTC)
thread_title:  Subscript d 

message: The expression is confusing. I don't think "Th is T with the addition of an inversion." Inversion? Maybe mirror plane? --MakecatTalk 04:03, 30 January 2012 (UTC)
thread_title:  Tetrahedron group 

message: What's the mathematical definition of a point group?  It would be nice for this page to include that.  This is not a mathematical definition:
: a crystallographic point group is a set of symmetry operations, like rotations or reflections, that leave a central point fixed while moving other directions and faces of the crystal to the positions of features of the same kind. 
Is a point group just a discrete subgroup of O(3), the group of rotations and reflections in 3 dimensions?  No, because then the symmetry group of a dodecahedron would be a point group.  Is it a discrete subgroup of O(3) that preserves some lattice?  I'm not sure.  Furthermore: when do two point groups count as "the same"?  When they're conjugate in O(3)?  Someone must know the answers.  Not me.  John Baez (talk) 08:08, 23 July 2016 (UTC)
thread_title:  What's a point group? 

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thread_title:  External links modified 

message: In section "The correspondence between different notations",  Cs is not explained anywhere.  From context, I assume it is the group generated by one horizontal reflection only?
Also V is not linked or explained.  Perhaps link to Klein_four-group#Geometry and edit that article to identify the the geometric representations D2,  C2h = D1d,  C2v = D1h with V, Vd, Vh, respectively, if this is the accepted notation?
Not sure enough to edit it myself... Chris2crawford (talk) 01:32, 11 September 2020 (UTC)
thread_title:  Cs and V,Vh,Vd