From owner-chemistry _-at-_)ccl.net Fri Mar 14 16:45:00 2008 From: "Michel PETITJEAN michel.petitjean%%cea.fr" To: CCL Subject: CCL: RE : Elegantly Describing Molecules with a Certain Geometric Property Message-Id: <-36508-080314121427-7794-yrRxjbvJtcRwTJeHponNoQ|server.ccl.net> X-Original-From: "Michel PETITJEAN" Content-class: urn:content-classes:message Content-Type: multipart/mixed; boundary="----_=_NextPart_001_01C885E3.F1FD2E11" Date: Fri, 14 Mar 2008 15:59:04 +0100 MIME-Version: 1.0 Sent to CCL by: "Michel PETITJEAN" [michel.petitjean~~cea.fr] This is a multi-part message in MIME format. ------_=_NextPart_001_01C885E3.F1FD2E11 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Do you mean: given the point group symmetry class and the representative = bond length then you would be able to generate the cartesian coordinates, up to a = direct isometry ? It seems to me that sulphur rings (Sn) have a representative bond length although torsonial angles may vary. May be you could refine the definition of the class of molecules that you are considering. Best regards, Michel Petitjean, DSV/iBiTec-S/SB2SM (CNRS URA 2096) CEA Saclay, bat. 528 91191 Gif-sur-Yvette Cedex Phone: +33(0)1 6908 4006 / Fax: +33(0)1 6908 4007 E-mail: michel.petitjean[A]cea.fr http://petitjeanmichel.free.fr/itoweb.petitjean.html -------- Message d'origine-------- De: Matthew Thompson matthew.thompson.:.nrl.navy.mil = [mailto:owner-chemistry[A]ccl.net] Date: ven. 14/03/2008 12:21 =C0: Michel PETITJEAN Objet : CCL: Elegantly Describing Molecules with a Certain Geometric = Property =20 Sent to CCL by: Matthew Thompson [matthew.thompson#nrl.navy.mil] Folks, I'm hoping there is a group theory savant or someone on this list = who can help me with a puzzle of mine. Namely, I'm trying to figure out = the best or most concise way to describe a set of molecules, maybe, if=20 possible, in group theoretical terms. The set I'm looking at is the set of all uni- and di-elemental molecules = that have *one* representative bond length. Obvious examples are all XY = and all X2 molecules; likewise, H2O, CH4, and SF6 also have one=20 characteristic bond length. Thus, I've been wondering if there was some way to describe these=20 molecules in a concise way with group theory. I can't say all Cnv and=20 Dnh work since N2O kills that (needs rNN and rNO to describe). I can't = say their point group must be Abelian because of Td and Oh (CH4 and = SF6). I think you could couch it in Z-matrix terms by saying you only need one = distance no matter the length of the Z-matrix (i.e., only one number in=20 the third column), but that seems sort of inelegant. It seems like=20 there must be some way to do this but I just can't figure it out. So, I = thought I'd ask CCL and probably get an answer in an instant. Thanks for any help, Matt --=20 Matt Thompson, PhD Naval Research Laboratory 202-767-2160 -=3D This is automatically added to each message by the mailing script = =3D-http://www.ccl.net/cgi-bin/ccl/send_ccl_messageSubscribe/Unsubscribe:=20Job: http://www.ccl.net/jobs=20Search Messages: http://www.ccl.net/htdig (login: ccl, Password: = search)http://www.ccl.net/spammers.txt------_=_NextPart_001_01C885E3.F1FD2E11--