From chemistry-request@server.ccl.net Tue Dec 22 01:44:41 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id BAA08409 for ; Tue, 22 Dec 1998 01:44:40 -0500 Received: from fen.bilkent.edu.tr (leo.fen.bilkent.edu.tr [139.179.97.92]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id BAA16824 Tue, 22 Dec 1998 01:40:36 -0500 (EST) Received: from gunser.fen.bilkent.edu.tr by fen.bilkent.edu.tr (5.65c/1.4IDA) id AA27124; Tue, 22 Dec 1998 08:41:34 +0300 Received: by gunser.fen.bilkent.edu.tr (SMI-8.6/SMI-SVR4) id IAA00920; Tue, 22 Dec 1998 08:38:09 +0200 Date: Tue, 22 Dec 1998 08:38:08 +0200 (EET) From: Ulrike Salzner To: Ben Cornett Cc: CCL Subject: Re: CCL:G:Linux vs Windows 95 vs Windows NT In-Reply-To: <367EA83B.B2073B80@emory.edu> Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear PC users, I am running G94 for a bit more than a year and G98 for about two month around the clock under Windows95. I never had a system crash. Only with G98 frequency calculations I sometimes get the message that the program has performed a illegal operation and will shut down (l1101). Therefore I think that stability is not a crucial problem. The most important point is, in my opinion, whether the performnace would be better with Linux. I was told figures between 50% faster to no difference, as suggested by Ben Cornett. Is there anybody who k n o w s rather than guesses how the two OSs compare? Gaussian is really easy to use under windows. Installation takes about ten minutes and than it runs without any problems. How much more can you wish for? Seasons Greetings, Uli Salzner =================================================================== Dr. Ulrike Salzner Department of Chemistry Tel.: (312) 290-2122 Bilkent University Fax.: (312) 266-5097 06533 Bilkent, Ankara e-mail: salzner@fen.bilkent.edu.tr Turkey ==================================================================== From chemistry-request@server.ccl.net Tue Dec 22 03:12:52 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id DAA08459 for ; Tue, 22 Dec 1998 03:12:52 -0500 Received: from ovrisc.mdche.u-szeged.hu (ovrisc.mdche.u-szeged.hu [160.114.101.224]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id DAA17422 Tue, 22 Dec 1998 03:08:48 -0500 (EST) Received: from localhost by ovrisc.mdche.u-szeged.hu (AIX 3.2/UCB 5.64/4.03) id AA18488; Tue, 22 Dec 1998 09:08:48 +0100 Date: Tue, 22 Dec 1998 09:08:47 +0100 (NFT) From: Kiss Gergo To: Ulrike Salzner Cc: CCL Subject: Re: CCL:G:Linux vs Windows 95 vs Windows NT In-Reply-To: Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII On Tue, 22 Dec 1998, Ulrike Salzner wrote: > > Dear PC users, > I am running G94 for a bit more than a year and G98 for about two month > around the clock under Windows95. I never had a system crash. Only with > G98 frequency calculations I sometimes get the message that the program > has performed a illegal operation and will shut down (l1101). Therefore I > think that stability is not a crucial problem. > > The most important point is, in my opinion, whether the performnace would be > better with Linux. I was told figures between 50% faster to no > difference, as suggested by Ben Cornett. Is there anybody who k n o w s > rather than guesses how the two OSs compare? > > Gaussian is really easy to use under windows. Installation takes about ten > minutes and than it runs without any problems. How much more can you wish > for? > > Seasons Greetings, > Uli Salzner > > =================================================================== > > Dr. Ulrike Salzner > > Department of Chemistry Tel.: (312) 290-2122 > Bilkent University Fax.: (312) 266-5097 > 06533 Bilkent, Ankara e-mail: salzner@fen.bilkent.edu.tr > Turkey > > ==================================================================== > --- "Windows was designed to keep the idiots away from Unix so we could hack in peace. Let's not break that." - Tom Christiansen (Perl Journal) Kiss Gergo PhD Student Szent-Gyorgyi Albert Orvostudomanyi Egyetem Orvosvegytani Intezet Albert Szent-Gyorgyi Medical University Department of Medical Chemistry H-6720 Szeged, Dom ter 8. (+36) 62-454-000/2889 From chemistry-request@server.ccl.net Tue Dec 22 03:33:31 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id DAA08504 for ; Tue, 22 Dec 1998 03:33:30 -0500 Received: from dirac.chem.jyu.fi (eloranta@dirac.chem.jyu.fi [130.234.8.4]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id DAA17481 Tue, 22 Dec 1998 03:29:32 -0500 (EST) Received: (from eloranta@localhost) by dirac.chem.jyu.fi (8.8.7/8.8.7) id KAA20328 for chemistry@www.ccl.net; Tue, 22 Dec 1998 10:29:24 +0200 From: Jussi Eloranta Message-Id: <199812220829.KAA20328@dirac.chem.jyu.fi> Subject: Re: CCL:G:Linux vs Windows 95 vs Windows NT To: chemistry@www.ccl.net Date: Tue, 22 Dec 1998 10:29:24 +0200 (EET) In-Reply-To: from "Ulrike Salzner" at Dec 22, 98 08:38:08 am Content-Type: text Dear Netters, One more advantage of using Linux is the good possibility for remote access (via modem or net). It is nice to monitor and start jobs from home ;-) Also for large installations cluster type of setups may be important which is another plus for Linux. The only thing I could think Linux is faster at is the hard disk access since Linux has better disk caching and drivers. BTW someone mentioned that windows version is easy to use but at least I find the windows more difficult to use than Linux. I depends what one has got used to, I guess. Try, for example, to do: % foreach dist (... large number of distances ....) > set energy = `fgrep UMP4\(SDQ\)= run-$dist.log | cut -c45-` > echo $dist $energy >> energy.dat > set hfc = `fgrep '2 H' run-$dist.log | tail -1 | cut -c36-47` > echo $dist $hfc >> hfc.dat > end with a mouse ;-) I would hate to do this kind of stuff with a simple text editor... (ok, some day I will learn perl..) Not to mention that complex stream of runs which require editing of input job after completing one computation cycle. Best regards, Jussi Eloranta ps. Linux is free too (apart from good fortran compiler) - windoze is not. From chemistry-request@server.ccl.net Tue Dec 22 07:11:40 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id HAA08703 for ; Tue, 22 Dec 1998 07:11:39 -0500 Received: from news.uni-kl.de (mmdf@news.uni-kl.de [131.246.137.51]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id HAA18344 Tue, 22 Dec 1998 07:07:38 -0500 (EST) Received: from iris1.chemie.uni-kl.de ( iris1.chemie.uni-kl.de [131.246.9.107] ) by news.uni-kl.de id aa22758 for ; 22 Dec 98 13:08 MET Received: from oktarin by iris1.chemie.uni-kl.de via SMTP (940816.SGI.8.6.9/940406.SGI.AUTO) for id NAA05479; Tue, 22 Dec 1998 13:07:31 +0100 Received: from localhost by oktarin with smtp (Smail3.1.28.1 #7) id m0zsQb6-0000FYC; Tue, 22 Dec 98 13:07 CET Date: Tue, 22 Dec 1998 13:07:32 +0100 (CET) From: Stefan Konietzny To: CCL Subject: Linux vs Windows 95 vs Windows NT In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear Gergo, >--- "Windows was designed to keep the idiots away from Unix so we could >hack in peace. Let's not break that." - Tom Christiansen (Perl Journal) > >Kiss Gergo PhD Student Szent-Gyorgyi Albert Orvostudomanyi Egyetem >Orvosvegytani Intezet Albert Szent-Gyorgyi Medical University Department >of Medical Chemistry H-6720 Szeged, Dom ter 8. (+36) 62-454-000/2889 Do you think that this is funny? I dont think so. People try to discuss the pros and cons of two operating systems and i think it helps noone to insult those who like to use Windows or who just want to know if it is worth to try g98w. The question is not what you love or hate, or what you think about people who use one or the other, but which experiences you have made. I hope the others who discussed this subject seriously agree with me. Merry Christmas to everyone, Stefan Konietzny. From chemistry-request@server.ccl.net Tue Dec 22 09:36:30 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id JAA08777 for ; Tue, 22 Dec 1998 09:36:29 -0500 Received: from euch6o.chem.emory.edu (euch6o.chem.emory.edu [170.140.39.144]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id JAA19299 Tue, 22 Dec 1998 09:32:27 -0500 (EST) Received: from emory.edu (localhost [127.0.0.1]) by euch6o.chem.emory.edu (950413.SGI.8.6.12/950213.SGI.AUTOCF) via ESMTP id JAA02022 for ; Tue, 22 Dec 1998 09:26:50 -0500 Sender: cornett@emory.edu Message-ID: <367FAC29.A30B0BA4@emory.edu> Date: Tue, 22 Dec 1998 09:26:49 -0500 From: Ben Cornett X-Mailer: Mozilla 4.06 [en] (X11; I; IRIX64 6.4 IP30) MIME-Version: 1.0 To: CCL Subject: Re: CCL:G:Linux vs Windows 95 vs Windows NT References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Stefan Konietzny wrote: > > Dear Gergo, > > >--- "Windows was designed to keep the idiots away from Unix so we could > >hack in peace. Let's not break that." - Tom Christiansen (Perl Journal) > > > >Kiss Gergo PhD Student Szent-Gyorgyi Albert Orvostudomanyi Egyetem > >Orvosvegytani Intezet Albert Szent-Gyorgyi Medical University Department > >of Medical Chemistry H-6720 Szeged, Dom ter 8. (+36) 62-454-000/2889 > > Do you think that this is funny? I dont think so. People try to discuss > the pros and cons of two operating systems and i think it helps noone to > insult those who like to use Windows or who just want to know if it is > worth to try g98w. > The question is not what you love or hate, or what you think about people > who use one or the other, but which experiences you have made. > I hope the others who discussed this subject seriously agree with me. > I agree. Let's not have yet another ridiculous OS holy war on this mailing list. Ben Cornett From chemistry-request@server.ccl.net Tue Dec 22 13:04:13 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id NAA08861 for ; Tue, 22 Dec 1998 13:04:13 -0500 Received: from smurf.chem.usu.edu (smurf.chem.usu.edu [129.123.3.85]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with SMTP id NAA23306 Tue, 22 Dec 1998 13:00:09 -0500 (EST) Received: from localhost (pczyryca@localhost) by smurf.chem.usu.edu (950413.SGI.8.6.12/950213.SGI.AUTOCF) via ESMTP id KAA04265 for ; Tue, 22 Dec 1998 10:01:34 -0800 Date: Tue, 22 Dec 1998 10:01:34 -0800 From: "Przemyslaw G. Czyryca" To: chemistry@www.ccl.net Subject: Re: CCL:G:Linux vs Windows 95 vs Windows NT In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII On Tue, 22 Dec 1998, Ulrike Salzner wrote: > Gaussian is really easy to use under windows. Installation takes about ten > minutes and than it runs without any problems. How much more can you wish > for? Easy accessibility from other hosts, for example. This makes your work much more efficient if you can check the results and start a new job, say, >from home on Sunday. Regards, * Przemek Czyryca, pczyryca@smurf.chem.usu.edu * From chemistry-request@server.ccl.net Tue Dec 22 16:07:38 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id QAA09372 for ; Tue, 22 Dec 1998 16:07:37 -0500 Received: from toucan.phy.bris.ac.uk (toucan.phy.bris.ac.uk [137.222.30.15]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id QAA26679 Tue, 22 Dec 1998 16:03:31 -0500 (EST) Received: from localhost (guido@localhost) by toucan.phy.bris.ac.uk (980427.SGI.8.8.8/980728.SGI.AUTOCF) via SMTP id VAA06114; Tue, 22 Dec 1998 21:02:26 GMT Date: Tue, 22 Dec 1998 21:02:26 +0000 (BST) From: Guido Germano Sender: guido@toucan.phy.bris.ac.uk Reply-To: Guido Germano To: Computational Chemistry List cc: Ahmed Bouferguene , Bill Ross , Wolfgang Roth , Jaromir Marek , Ned Martin , Ning Xie , Szieberth Denes , Sigismondo Boschi , Larry Cuffe Subject: G: Summary: shmget failed on SGI Message-ID: Organization: Physics Department University of Bristol MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII The problem: g94 D4 compiled on a SGI R10000 with the 7.2.1 compiler and the 6.5.1 OS revision core dumps with the error message "shmget failed". The solution, due to Joe Ochterski, one of the authors of g98: compile with the flag -OPT:reorg_common=OFF. This flag is necessary with SGI compilers more recent than g94 D4, and is present in g98 A6. Add :reorg_common=OFF to the second line starting with ROF after # R10000 in bsd/sgi.make. Comment: there are other less elegant workarounds as launching a shell that calls clearipc every 5' (works only for scalar execution though) or increasing the shmmax kernel parameter. The latter might be underdimensioned on IRIX 6.4 (less than 25% of the total RAM), but on 6.5 it is already set by default to 80% of the total RAM: see Appendix 1 of the IRIX Admin: System Configuration and Operation manual and the file /var/sysgen/mtune/kernel. After upgrading the OS to 6.5.2 the next problem was around the corner: g94/98 gave lots of segv (segmentation violations). Joe was at help again, telling me that it is a known bug of the mp libraries that won't be fixed before 6.5.3. The workaround for the meanwhile is setenv MP_STACK_OVERFLOW OFF Thanks to all others who replied; they're in cc. Apologies for the late summary. Guido Germano University of Bristol, +44-117-928 9000 ext. 8755 http://www.phy.bris.ac.uk/staff/germano_g.html From chemistry-request@server.ccl.net Tue Dec 22 18:52:52 1998 Received: from www.ccl.net (www.ccl.net [192.148.249.5]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id SAA09789 for ; Tue, 22 Dec 1998 18:52:52 -0500 Received: from alchemy.chem.utoronto.ca (alchemy.chem.utoronto.ca [142.150.224.224]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id SAA27842 Tue, 22 Dec 1998 18:48:43 -0500 (EST) Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.7.4/8.7.3) id SAA03419 for chemistry@www.ccl.net; Tue, 22 Dec 1998 18:48:43 -0500 (EST) Date: Tue, 22 Dec 1998 18:48:43 -0500 (EST) From: "E. Lewars" Message-Id: <199812222348.SAA03419@alchemy.chem.utoronto.ca> To: chemistry@www.ccl.net Subject: SUMMARY OF CALCULATION OF RATE CONSTANT 1998 Dec 22, Tuesday Here is the summary of replies to my question about calculating rate constants QUESTION =========== > Tued 1998 Dec 15 > > Subject: Calculating rate constant > > Hello, > Has anyone any suggestions for a fairly easy way to calculate a rate constant > using Gaussian? I want to avoid the intricacies of RRKM theory and just get > a k_rate accurate to within a factor of, say, 10. For example, consider > > HNC ---> HCN > > At some temp T HNC in, say, the gas phase (or nonpolar solvent?) has a > certain halflife (=ln2/k_r). It's easy to calculate a good number for the > activation energy, but what's a simple way to estimate a realistic k_r (and > thus t_1/2)? ============= 1998 DEC ca. 15 CALC RATE CONST ANSWERS #1 Subject: Re: CCL:G:CALCULATING A RATE COSTANT To: elewars@alchemy.chem.utoronto.ca (E. Lewars) Date: Tue, 15 Dec 1998 15:29:54 -0500 (EST) Cc: topper@cooper.edu (TOPPER ROBERT) Hi, I'm not an expert in this field, but my understanding is that getting rate constants right to within an order of magnitude is the current state-of-the-art. Tunneling is surely an important contribution to the kinetics of HCN <=> HNC, which can easily change the rate constant by several orders of magnitude compared to the classical answer. Moreover, tiny errors in the activation energy amount to huge effects on the equilibrium constant, requiring a very accurate calculation of the activation energy (i.e. using correlated methods). Don Truhlar, for whom I worked many years ago, is one of the real experts in this field. Check out one of his more recent reviews, or check out his web page at http://comp.chem.umn.edu/WWW/Truhlar/Truhlar.html for information about GAUSSRATE, which interfaces with Gaussian to do transition-state theory calculations of chemical reactions, including tunneling and other effects. The code is easy to use and REALLY well documented (for example, one of my undergrads installed POLYRATE, ran its test suite, and hooked it up to a potential energy surface from the literature successfully). Best regards, Robert Topper ***************************************************************************** Robert Q. Topper email: topper@cooper.edu Assoc. Professor of Chemistry phone: (212) 353-4378 The Cooper Union fax: (212) 353-4341 51 Astor Place subway: take the 6 to Astor Place New York, NY 10003 and you're there! http://www.cooper.edu/engineering/chemechem/ ***************************************************************************** The Cooper Union for the Advancement of Science and Art is a tuition-free college in Greenwich Village, at Cooper Square and Astor Place. ***************************************************************************** ============= #2 Qiang Cui First of all, you will need a reasonably accurate barrier height and reaction coordinate. I guess u will need to push your method a little bit to get it right for the particular HNC/HCN system, 'cause you are breaking the triple bond and electron correlation effect should be significant. But there should be enough data in the literature, 'cause it's one of the favorable system for people doing quantum dynamics. Read some paper from Prof. J. Bowman, who did CCSD(T) level PES and some complex L2 etc. as well. As to the isomeration rate constant, I guess a decent approach is VTST with semi-classical tunneling, 'cause tunneling should be significant for your system. You can also try the approximate instaton approach, which appear to be rather accurate as well for tunneling splittings and rate constant etc. Any way, POLYRATE and DOIT are the program packages for the above two approaches, respectively. Finally, as mentioned above, if you want to push the limit, do the quantum mechanical calculations. The paper by Bowman and co-workers should be very useful references. Good luck. ___________________________________________________________________________ Qiang Cui Dept. of Chem. _ __..-;''`--/'/ /.',-`-. Harvard Univ. (`/' ` | \ \ \\ / / / / .-'/`,_ 12 Oxford St., /'`\ \ | \ | \| // // / -.,/_,'-, Cambridge, MA 02138 /<7' ; \ \ | ; ||/ /| | \/ |`-/,/-.,_,/')(617)-495-8997 / _.-, `,-\,__| _-| / \ \/|_/ | '-/.;.\' (617)-495-1775 `-` f/ ; / __/ \__ `/ |__/ | Fax: (617)-496-3204 `-' | -| =|\_ \ |-' | http://yuri.harvard.edu/~qiang __/ /_..-' ` ),' // qiang@tammy.harvard.edu ((__.-'((___..-'' \__.' 805 Mt. Auburn Street Apt. 35 Watertown, MA 02472 (617)-926-6027 __________________________________________________________________________ ============== #3 theis@kalium.kiku.dk Date: Wed, 16 Dec 1998 08:25:32 +0100 To: elewars@alchemy.chem.utoronto.ca Subject: rate constant Hi, I believe a very simple approach to the problem would be to use simple transition state theory i.e. ln(k)=-DeltaH/RT+DeltaS/R, the thermodynamic quantities corresponds to the enthalpy and entropy of activation respectively (e.g DeltaH=H(TS)-H(reactant)) in addition see Atkins Physical Chemistry. You can derive all these numbers extremely easy from the gaussian - Thermochemisty - section in a frequency run. I know that at least a couple of the quantities are obtainable from a J. Am. Chem. Soc. paper by A. Chalk and L. Radom some time late 1996 to mid 1997. I hope this helps. Cheers, Theis * Mr. Theis Ivan Solling Department of Chemistry University of Copenhagen DK-2100 Copenhagen Ph. 45-3235-0187/Fax. 45-3532-0212 ================= #4 Date: Wed, 16 Dec 1998 13:52:25 -0800 Reply-To: E.Tajkhorshid@DKFZ-Heidelberg.de To: "E. Lewars" Subject: Re: CCL:G:CALCULATING A RATE COSTANT Just to ask for the summary. -- Emad ********************************************************************* E. Tajkhorshid, Ph.D. German Cancer Research Center; DKFZ Tel: +49 6221 42 2340 Dept. Molecular Biophysics (H0200) FAX: +49 6221 42 2333 P.O.Box 101949 69009 Heidelberg, Germany Email: E.Tajkhorshid@DKFZ-Heidelberg.de ********************************************************************* * "Meeting science is meeting scientist" * ********************************************************************* =========== #5 Dec 16 Sergiusz Kwasniews (75) Re: CCL:G:CALCULATING A RATE COSTANCommand: Read MessageMessage 9/11 from Sergiusz Kwasniewski Dec 16 '98 at 4:26 pm Date: Wed, 16 Dec 1998 16:26:51 +0100 (MET) To: "E. Lewars" Subject: Re: CCL:G:CALCULATING A RATE COSTANT perhaps you could use TST (transition state theory) we use it as an extra way for calculating rate constants ... instead of using DOS (density of states) it utilises partition functions. the theory behind this is less complicated, if you already have some ideas about statistical thermodynamics bye S. Kwasniewski ****************************** Sergiusz P. Kwasniewski Erfken 1 3530 Houthalen-Helchteren Belgium Tel. (+32) (0)11/52.66.52 Limburgs Universitair Centrum Universitaire Campus, Gebouw D 3590 Diepenbeek Tel. (+32) (0)11/26.83.15 Fax. (+32) (0)11/26.83.01 e-mail: skwasnie@luc.ac.be =========== #6 Sender: jvilla Date: Wed, 16 Dec 1998 18:50:45 +0100 To: "E. Lewars" Subject: Re: CCL:G:CALCULATING A RATE COSTANT you can use GAUSSRATE, which an interface between Gaussian and Polyrate, for doing this calculations. The program is very easy to use for your purposes and also for including tunneling in the calculations. You can get it at: http://comp.chem.umn.edu/gaussrate/ Jordi E. Lewars wrote: > Tued 1998 Dec 15 > >Subject: Calculating rate constant > > Hello, > Has anyone any suggestions for a fairly easy way to calculate a rate constant > using Gaussian? I want to avoid the intricacies of RRKM theory and just get > a k_rate accurate to within a factor of, say, 10. For example, consider > > HNC ---> HCN > > At some temp T HNC in, say, the gas phase (or nonpolar solvent?) has a > certain halflife (=ln2/k_r). It's easy to calculate a good number for the > activation energy, but what's a simple way to estimate a realistic k_r (and > thus t_1/2)? > > Thanks > E. Lewars ------------- Jordi Vill`a Research Group on Medical Informatics Carrer del Doctor Aiguader 80 E-08003 Barcelona Tlf: 34-93-2211009 Fax: 34-93-2213237 jvilla@imim.es http://www1.imim.es/~jvilla ================ ================= #7 DFHakala@aol.com Date: Wed, 16 Dec 1998 20:42:00 EST To: elewars@alchemy.chem.utoronto.ca Subject: Re: CCL:G:CALCULATING A RATE COSTANT While Gaussian or whatever QM program can be used to generate a potential energy surface, and you could take your initial reactant as defined by some point on that multidimensional PES and using a path of least action thru a transition state go to the final product point and estimate an activation energy, without an understanding of how energy is partitioned amongst the degrees of freedom of the molecule and how those degrees of freedom couple and how energy can flow statistically among those degrees of freedom to provide enough energy to go over the barrier(s) presented by the transition states (in other words apply RRKM) I do not believe you can arrive at a meaningful rate constant other than by sheer luck. Anything more complicated than diatomics gets tricky fast. To perform an a priori calculation of a polyatomic rate constant for dissociation or rearrangement would require a set of QM calculations as a necessary, but not sufficient requirement. ============ #8 Dec 16 Ning Xie (62) Re: CCL:G:CALCULATING A RATE COSTANCommand: Read MessageMessage 5/7 from Ning Xie Dec 16 '98 at 8:42 pm Subject: Re: CCL:G:CALCULATING A RATE COSTANT In-reply-to: <199812151757.MAA02387@alchemy.chem.utoronto.ca> To: "E. Lewars" Message-id: MIME-version: 1.0 Content-type: TEXT/PLAIN; charset=US-ASCII Hi, there, Could you forward me the replies to your question please? Thank you very much. ning _______________________________________________________________ | NING XIE Tel: (781)245-7954 | | 31 Sweetser St. Fax: (781)245-7954 | | Wakefield, MA e-mail: xiening@meena.cc.uregina.ca | | 01880 ning_xie@yahoo.com | --------------------------------------------------------------- ============