From chemistry-request@server.ccl.net Sat Aug 12 04:00:29 2000 Received: from mb03.swip.net (mb03.swip.net [193.12.122.217]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id EAA04932 for ; Sat, 12 Aug 2000 04:00:28 -0400 Received: from [212.151.36.18] (d212-151-36-18.swipnet.se [212.151.36.18]) by mb03.swip.net (8.8.8/8.8.8) with ESMTP id JAA00174; Sat, 12 Aug 2000 09:58:37 +0200 (MET DST) X-Sender: peo@compchem.dfh.dk (Unverified) Message-Id: In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Sat, 12 Aug 2000 10:04:48 +0200 To: CHEMISTRY@ccl.net From: Per-Ola Norrby Subject: Re: CCL:Vibrational analysis w/ constraints David and Jan, The reason that determining vibrations at non-stationary points is "meaningless" is because forces must be assumed to be zero in the analysis. If you can get rid of the force, the analysis can be performed without problem. Handy and coworkers showed how to project out the gradient vector a long time ago (1982, I believe, but I don't have the reference handy :-). There are several reasons to do such an analysis. I'm interested in cases where the free energy transition state does not correspond to the PES maximum. Projecting out the forces (and the translational and rotational modes) before determining the thermodynamic contributions is just as valid as doing it at a TS, where you also ignore 7 degrees of freedom. The force vector in the first case corresponds to the reaction coordinate in the second. I'm also interested in using the method to create projected MM force fields for non-stationary points. Best, Per-Ola Norrby * Per-Ola Norrby, Dept. of Med. Chem., Danish School of Pharm. * peo@dfh.dk, peo@compchem.dfh.dk, http://compchem.dfh.dk/PeO/ * tel. +45-35306506, fax +45-35306040 David Power wrote: >Jan, > If you mean you want to perform a second-derivative vibrational >frequency analysis on a geometry obtained from a partial geometry >optimization, I have a couple of responses. To my knowledge there is no >way to do such a thing with Gaussian. But, more importantly, why would >you want to do such a thing? A vibrational analysis at some point, other >than an extrema, is totally meaningless. The stationary point obtained >>from a partial geometry optimization is not a true stationary point at >all. > >Cheers, >David Power >Department of Chemistry >University of North Texas >NT Station, Box 305070 >Denton, TX 76203-5070 >tdp0006@unt.edu > > >On Fri, 11 Aug 2000, Jan H. Jensen wrote: > >> Hi, >> I am interested in doing a vibrational analysis of a Hessian matrix >> calculated for a system that was optimized with geometric constraints. Can >> anyone point me to literature of this subject? >> >> Thanks, Jan Jensen >> >> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- >> Jan H. Jensen Assistant Professor >> Department of Chemistry jan-jensen@uiowa.edu >> University of Iowa Phone:(319) 335-1108 >> Iowa City, IA 52242 FAX: (319) 335-1270 >> http://www.uiowa.edu/~chemdept/faculty/jensen/ >> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- >> >> >> >> >> >> >> >> >> > > >-= This is automatically added to each message by mailing script =- >CHEMISTRY@ccl.net -- To Everybody | CHEMISTRY-REQUEST@ccl.net -- To >Admins >MAILSERV@ccl.net -- HELP CHEMISTRY or HELP SEARCH >CHEMISTRY-SEARCH@ccl.net -- archive search | Gopher: gopher.ccl.net 70 >Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl@ccl.net From chemistry-request@server.ccl.net Sat Aug 12 21:42:38 2000 Received: from mcmail.cis.McMaster.CA (mattacf@mcmail.CIS.McMaster.CA [130.113.64.66]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id VAA01709 for ; Sat, 12 Aug 2000 21:42:37 -0400 Received: from localhost (mattacf@localhost) by mcmail.cis.McMaster.CA with ESMTP id VAA26096; Sat, 12 Aug 2000 21:37:44 -0400 (EDT) Date: Sat, 12 Aug 2000 21:37:44 -0400 (EDT) From: "C.F. Matta" To: Yubo Fan cc: CHEMISTRY@ccl.net Subject: Re: CCL:Agostic interaction In-Reply-To: <39923710.F04644B0@guomai.sh.cn> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Hi Dr. Fan, Check also article: Popelier P.L.A. and Logothetis G. "Characterization of an agostic bond on the basis of the electron density". J. Organometallic Chem. Vol. 555, pp.101-111 (1998). Cheers, Cherif F. Matta ___________________________________________________________________________ Cherif F. Matta tel. (905) 525-9140 ext. 22502 Chemistry Department fax (905) 522-2509 McMaster University _______________________ Hamilton, Ontario, CANADA L8S 4M1. | "Choice not chance ....................................................| determines one's Member of the Board of Governors of the University | destiny". Anonymous ___________________________________________________________________________ On Thu, 10 Aug 2000, Yubo Fan wrote: > Hi, All CCLers, > > I have met a keyword, agostic interaction, recently. It cannot be found > in various dictionaries. To my knowledge, it means weak intermolecular > interaction. I really don't understand it clearly. The problem is what > types of intermolecular interactions can be regarded as agostic > interaction. Could anybody give me the definition and examples? > > Thanks in advance > > Y. Fan > > -- > ============================================================= > Yubo Fan Email: yubofan@guomai.sh.cn > Organic Synthesis Lab > The Department of Chemistry > Fudan University Phone: 8621-65648139 > No. 220 Handan Road Fax: 8621-65641740 > Shanghai, 200433 > P. R. China > ============================================================= > > > > > -= This is automatically added to each message by mailing script =- > CHEMISTRY@ccl.net -- To Everybody | CHEMISTRY-REQUEST@ccl.net -- To Admins > MAILSERV@ccl.net -- HELP CHEMISTRY or HELP SEARCH > CHEMISTRY-SEARCH@ccl.net -- archive search | Gopher: gopher.ccl.net 70 > Ftp: ftp.ccl.net | WWW: http://www.ccl.net/chemistry/ | Jan: jkl@ccl.net > > > > > >