If you want to have a rant, just have a look at the wikipedia page for single-layer materials.
Phosphorene is particularly egregious: https://en.wikipedia.org/wiki/File:Phosphorene_structure.png On Fri, 30 Dec 2022 at 20:30, Radovan Cerny <radovan.ce...@unige.ch> wrote: > OK, I understand. Thank you Mike. > > The graphene is then 2P material with the layer group p6/mmm. Can somebody > give me an example of a 2D material with the plane group p6mm? > > Thank you > > Radovan > > Radovan Cerny > Laboratoire de Cristallographie > Université de Genève > 24, quai Ernest-Ansermet > CH-1211 Geneva 4, Switzerland > Phone : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08 > mailto : radovan.ce...@unige.ch > URL : http://www.unige.ch/sciences/crystal/cerny/rcerny.htm > ------------------------------ > *De :* Mike Glazer <mike.gla...@physics.ox.ac.uk> > *Envoyé :* vendredi 30 décembre 2022 12:20 > *À :* Radovan Cerny <radovan.ce...@unige.ch>; Matthew Rowles < > rowle...@gmail.com> > *Cc :* RIETVELD_L Distribution List <rietveld_l@ill.fr> > *Objet :* Re: "2d materials don't exist" editorial?? > > Radovan > Not quite. Graphene is a 3d material but has periodicity in 2d making its > symmetry given by one of the 80 subperiodic layer groups. > Mike Glazer > > Get Outlook for Android <https://aka.ms/AAb9ysg> > ------------------------------ > *From:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> on behalf > of Radovan Cerny <radovan.ce...@unige.ch> > *Sent:* Friday, December 30, 2022 11:07:52 AM > *To:* Matthew Rowles <rowle...@gmail.com> > *Cc:* RIETVELD_L Distribution List <rietveld_l@ill.fr> > *Subject:* RE: "2d materials don't exist" editorial?? > > Thank you Matt, > > for bringing this subject which I have never taken too seriously, butt as > Massimo pointed out in his paper, there are important differences in what > symmetry allows for 2D and what for 2P, for example. > > I feel now a bit responsible, because my colleagues at the Quantum matter > dpt. at UNIGE are working on layered pnictides and call them always 2D > materials, which is not correct. They are 2P materials. I will try to > educate them now, even if I am retired. Maybe they can call them 2D > materials if they talk about the physical properties rather than about the > structure? > I have already tried to introduce then in the OD theory for polytypic > structures, but without too much success. They prefer to do their DFT > modelling rather than have a look on what has been already done. > > A test, whether I have properly understood Massimo: Graphen is 2D > material, but when I attach anything to it or take more than one layer of > graphen, it becomes 2P material, right? > > Have a nice end of the year > > Radovan > > Radovan Cerny > Laboratoire de Cristallographie > Université de Genève > 24, quai Ernest-Ansermet > CH-1211 Geneva 4, Switzerland > Phone : [+[41] 22] 37 964 50, FAX : [+[41] 22] 37 961 08 > mailto : radovan.ce...@unige.ch > URL : http://www.unige.ch/sciences/crystal/cerny/rcerny.htm > ------------------------------ > *De :* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> de la part > de Matthew Rowles <rowle...@gmail.com> > *Envoyé :* lundi 26 décembre 2022 11:08 > *À :* Alan W Hewat <alan.he...@neutronoptics.com> > *Cc :* Leopoldo Suescun <leopo...@fq.edu.uy>; RIETVELD_L Distribution > List <rietveld_l@ill.fr> > *Objet :* Re: "2d materials don't exist" editorial?? > > These are good learning events. > > . > > And it doesn't make much third dimensional periodicity to make a layered > material act as a bulk 3d material (see recent publications by Kate > Putman), or at least from a powder diffraction point of view. > > > > > On Sun, 25 Dec 2022, 12:40 Alan W Hewat, <alan.he...@neutronoptics.com> > wrote: > > Symmetry is the Crystallographer's first love, but periodicity is more > important in deciding to call a structure 2D or 3D. Powder diffraction in > particular showed that symmetry is ephemeral in many materials, whose > symmetry is lowered when they are cooled. This symmetry is just the > consequence of averaging over time and space. Yet we remain fascinated by > symmetry, sometimes imposing it on Nature when it has no physical > consequences. > > Great to have a little philosophy to go with the Christmas pudding. Thanks > Mathew. > ________________________________ > Dr Alan Hewat, NeutronOptics > Grenoble, FRANCE (from phone) > alan.he...@neutronoptics.com > +33.476984168 VAT:FR79499450856 > http://NeutronOptics.com/hewat > _______________________________ > > > On Sun, 25 Dec 2022, 01:16 Matthew Rowles, <rowle...@gmail.com> wrote: > > I didn't even know of the existence of the frieze, rod, and layer groups > until I read this comment. > > So, I guess it's working? > > On Sat, 24 Dec 2022, 22:49 Leopoldo Suescun, <leopo...@fq.edu.uy> wrote: > > Hi all, > > Thank you Matt for bringing up this issue. > > Massimo Nespolo has been fighting for the correct description of > structures, specially focusing on symmetry and proper terminology, for > years (see his many articles on the misuse of lattice, sublattice, > superlattice, etc). > > He has, as well, been educating crystallographers of all ages in symmetry > concepts and use through IUCr's MaThCryst Commision and Internationa School > on Fundamental Crystallograpy courses around the world. > > He'll probably be remembered by many as a Dick Marsh of symmetry. > > I guess it is the task of all us, crystallographers, to promote the > correct use of terminology related to crystal structures, as suggested by > IUCr conventions included in IUCr Dictionary and modern literature. > https://dictionary.iucr.org/Main_Page > > Best wishes for all of you that, in a way or another have this as a > special week in your calendars, and Happy New Year for all. > > Leo > > El sáb, 24 de dic. de 2022 05:01, Matthew Rowles <rowle...@gmail.com> > escribió: > > Hi all > > I think this is the one > > https://scripts.iucr.org/cgi-bin/paper?S1600576721001606 > > Matthew > > On Fri, 23 Dec 2022, 10:00 Matthew Rowles, <rowle...@gmail.com> wrote: > > This might be it, but the link is to the iucr homepage: > > Google: "letter to the editor" two-dimensional "layer groups" graphene iucr > > [image: image.png] > > > > > On Fri, 23 Dec 2022 at 09:53, Matthew Rowles <rowle...@gmail.com> wrote: > > Hi all > > A while ago (months, years??) I recall reading an editorial or letter to > the editor about materials being referred to as "2D", and how they're > actually 3D, and just periodic in the plane, and should be referred to as > 2P and a relevant layer group. > > Does anyone recall such a thing? > > > Thanks > > Matthew > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <alan.he...@neutronoptics.com > > > Send commands to <lists...@ill.fr> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <alan.he...@neutronoptics.com > > > Send commands to <lists...@ill.fr> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/rietveld_l@ill.fr/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > >
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
