In fact there's another good reason not to use H3 etc when you mean R3: the H lattice symbol is already in use to mean something completely different! - namely H-centring in *trigonal & hexagonal* (i.e. *not rhombohedral*) space groups such as P3, P3/1 etc & supergroups, so e.g. H3 is actually a supergroup of P3 not R3.
See here: http://books.google.co.uk/books?id=ilVvOYOFCx8C&pg=PA96 and here: http://img.chem.ucl.ac.uk/sgp/large/trigonal.htm and the above is consistent with the definition now adopted in the new ITC-A1: http://it.iucr.org/cgi-bin/itsearch?query=DC.creator%3D%22H.%22%20AND%20 DC.creator%3D%22Wondratschek%22&metaname=swishdefault&IT.group=2.1.4&IUC r.volume=A1 It would be interesting to know if the PDB consulted the IUCr on this change! -- Ian > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Bernhard Rupp > Sent: 27 October 2008 22:50 > To: CCP4BB@JISCMAIL.AC.UK > Subject: H32 use > > Dear All, > > I wonder whether it is a good idea to still accept H32 as > a space group in the PDB CRYST1 record, despite it may be used > internally by programs. > > * The combination of hexagonal cell parameters and R32 clearly > indicates a hexagonal (obverse) axis setting in the R centered cell. > > * The H-M R32 symbol with rhombohedral setting a, alpha, is > inconsistent > anyhow because the cell is then primitive and not centered. > > * The ITCA (and most data mining programs?) seem to be > unaware of a Bravais symbol H. > > The practice of using H32 anywhere in published data should be > strongly discouraged. Internally please feel free to use whatever > works. > > What is the current opinion on this? > > Best, BR > ----------------------------------------------------------------- > Bernhard Rupp > 001 (925) 209-7429 > +43 (676) 571-0536 > [EMAIL PROTECTED] > [EMAIL PROTECTED] > http://www.ruppweb.org/ > ----------------------------------------------------------------- > The hard part about playing chicken > is to know when to flinch > ----------------------------------------------------------------- > > Disclaimer This communication is confidential and may contain privileged information intended solely for the named addressee(s). It may not be used or disclosed except for the purpose for which it has been sent. If you are not the intended recipient you must not review, use, disclose, copy, distribute or take any action in reliance upon it. If you have received this communication in error, please notify Astex Therapeutics Ltd by emailing [EMAIL PROTECTED] and destroy all copies of the message and any attached documents. Astex Therapeutics Ltd monitors, controls and protects all its messaging traffic in compliance with its corporate email policy. The Company accepts no liability or responsibility for any onward transmission or use of emails and attachments having left the Astex Therapeutics domain. Unless expressly stated, opinions in this message are those of the individual sender and not of Astex Therapeutics Ltd. The recipient should check this email and any attachments for the presence of computer viruses. Astex Therapeutics Ltd accepts no liability for damage caused by any virus transmitted by this email. E-mail is susceptible to data corruption, interception, unauthorized amendment, and tampering, Astex Therapeutics Ltd only send and receive e-mails on the basis that the Company is not liable for any such alteration or any consequences thereof. Astex Therapeutics Ltd., Registered in England at 436 Cambridge Science Park, Cambridge CB4 0QA under number 3751674
