From chemistry-request@server.ccl.net Tue Dec 8 10:00:26 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 KAA03764 for ; Tue, 8 Dec 1998 10:00:18 -0500 Received: from moorea.uni-muenster.de (MOOREA.UNI-MUENSTER.DE [128.176.126.33]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id JAA15179 Tue, 8 Dec 1998 09:54:57 -0500 (EST) Received: from localhost (chan@localhost) by moorea.uni-muenster.de (8.8.7/8.7.5) with ESMTP id OAA20776 for ; Tue, 8 Dec 1998 14:54:16 GMT Date: Tue, 8 Dec 1998 15:54:15 +0100 (MEZ) From: "Jerry C.C. Chan" To: CHEMISTRY@www.ccl.net Subject: J-coupling tensor In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear Netters, Could anyone tell me what softwares (commercial or not) can calculate the J coupling (scalar coupling) tensor between two nuclei in a molecule? Thanks, Jerry ****************************************************************** * Jerry Chun Chung CHAN chan@uni-muenster.de * * Universitaet Muenster phone: 0049-251-83-29156 * * Institut fuer Physikalische Chemie fax: 0049-251-83-29159 * * Schlossplatz 4-7 * * D-48149 Muenster * * Germany * ****************************************************************** From chemistry-request@server.ccl.net Tue Dec 8 14:16:25 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 OAA03824 for ; Tue, 8 Dec 1998 14:16:25 -0500 Received: from risky3.thchem.siu.edu (risky3.thchem.siu.edu [131.230.89.13]) by www.ccl.net (8.8.3/8.8.6/OSC/CCL 1.0) with ESMTP id OAA17697 Tue, 8 Dec 1998 14:11:05 -0500 (EST) Received: from localhost (tapas@localhost) by risky3.thchem.siu.edu (AIX4.2/UCB 8.7/8.7) with SMTP id NAA18570 for ; Tue, 8 Dec 1998 13:15:24 -0600 (CST) Date: Tue, 8 Dec 1998 13:15:23 -0600 (CST) From: Tapas Kar To: "Comp. Chem. List" Subject: G94/g98 performance Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII After upgrading my rs60000-590 box to 595, I found only 12-15% improvement on G94/g98 jobs(Mp2, cis-mp2 etc). At the HF level(scf=direct) i am getting 25-30%. At the higher level calculations it seems performance is poor. It is not clear where is the bottleneck. I like to know the experience of others using 595 model of rs60000 and g94/g98. Tapas -------------------------------------------- From chemistry-request@server.ccl.net Tue Dec 8 15:09:37 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 PAA03871 for ; Tue, 8 Dec 1998 15:09:36 -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 PAA18277 Tue, 8 Dec 1998 15:04:16 -0500 (EST) Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.7.4/8.7.3) id PAA11484 for chemistry@www.ccl.net; Tue, 8 Dec 1998 15:04:17 -0500 (EST) Date: Tue, 8 Dec 1998 15:04:17 -0500 (EST) From: "E. Lewars" Message-Id: <199812082004.PAA11484@alchemy.chem.utoronto.ca> To: chemistry@www.ccl.net Subject: ANSWERS TO F AS A PROBLEM ELEMENT Tues 1998 Dec 8 Hello, these are the replies to my question about F as a problem element (it turns out other halogens can also give problems--see H2C=CCl2, below). Thanks very much to all who helped. E. Lewars ------------------ QUESTION: >(1) Does anyone have any refs to document the view that in ab initio >calc's > F is a problem element--for example, that optimization of fluorine- > containing molecules does not readily give good geometries (or energies?)? > I have refs to FOOF and to F2; any instances of other troublesome > F-containing species would be welcome. ========== ANSWERS (if any one has been omitted, this is entirely my carelessness): #1 See: Dixon & Feller in J. Phys. Chem. A 102, 8209-16 (1998). They discuss heats of formation for CF2, FCO and CF2O - lots of high-end data included. !!!!!!! thru Dec. 18 please use the following address: !!!!!!!!! E-mail: paneth@kemi.uu.se ************************************************************************** Piotr Paneth, Ph.D., D.Sc. Professor of Chemistry Technical University, Zeromskiego 116, 90-924 Lodz, Poland phone: (+48-42) 631-3199 fax: (+48-42) 636-5008 > ============== #2 Subject: Re:CCL:F AS PROBLEM ELEMENT; A COULSON QUOTE I have also been advised that F, and other halogens for that matter are often problem elements. I have been looking at the replacements for various ozone depleting substances (Freons, Halons) and have done the following sample calculations using Gaussian 94. H2C=CCl2 C=C C-H C-X C-C-X Experiment 1.32 1.73 123 Mopac AM1 1.335 1.099 1.699 122.3 Mopac PM3 1.33 1.086 1.682 122.7 HF-STO 3G 1.311 1.083 1.777 122.7 HF-6-31G 1.309 1.071 1.786 123.1 HF-6 311++G(3df,2pd) 1.307 1.071 1.721 122.8 <--big basis! HF-LANL2DZ 1.318 1.071 1.783 123 B3LYP-LANL2DZ 1.338 1.085 1.803 123 These results suggest that the very large 6-311++G (3df,2pd) basis set offers the best predictive structure particularly in estimating the critical C=C and C-Cl bonding properties. I would appreciate receiving copies of any references which may result from your quiry. Regards Doug Dierdorf Applied Research Associates, Inc. ; Thu, 26 Nov 1998 14:24:37 -0700 (MST) ==================== #3 F3- is troublesome: JPC 96 4359 (1992) F- in water clusters needed high levels of theory (work in Dr Malcolm's group) Dr Nok Malcolm Theory Group Dept of Chem U of Manchester Oxford Road, Manchester noj.malcolm@man.ac.uk ===================== #4 The largest deviation from exp with the G2 method occur for molecules with halogens: L. A. Curtis, K. Raghavachari, P. C. Redfern, J. A. Pople, JCP 106 1063 (1997) (EL) =========== From chemistry-request@server.ccl.net Tue Dec 8 15:10:34 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 PAA03915 for ; Tue, 8 Dec 1998 15:10:34 -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 PAA18299 Tue, 8 Dec 1998 15:05:13 -0500 (EST) Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.7.4/8.7.3) id PAA11534 for chemistry@www.ccl.net; Tue, 8 Dec 1998 15:05:14 -0500 (EST) Date: Tue, 8 Dec 1998 15:05:14 -0500 (EST) From: "E. Lewars" Message-Id: <199812082005.PAA11534@alchemy.chem.utoronto.ca> To: chemistry@www.ccl.net Subject: ANSWER TO COULSON QUOTE 1998 Nov 25 Hello, Hello, Thanks to all who helped with the Coulson quote: Someone, I think it may have been Coulson, said, ca. 1952, that calculating the energy differenece between two isomers as the difference in their computed energies is like weighing the captain by weighing the ship with and without him. I would appreciate the reference to this statement. [Of course in the 1950's few dreamt that it would ever be possible to calculate energy differences to chemical accuracy, at least by ab initio methods]. Thanks E. Lewars ========================== ANSWER: Coulson, "Valence", 2nd ed., Oxford U Press, 1961, p. 91 ============= From chemistry-request@server.ccl.net Tue Dec 8 21:19:54 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 VAA04334 for ; Tue, 8 Dec 1998 21:19:54 -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 VAA04641 Tue, 8 Dec 1998 21:14:31 -0500 (EST) Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.7.4/8.7.3) id VAA27830 for chemistry@www.ccl.net; Tue, 8 Dec 1998 21:14:31 -0500 (EST) Date: Tue, 8 Dec 1998 21:14:31 -0500 (EST) From: "E. Lewars" Message-Id: <199812090214.VAA27830@alchemy.chem.utoronto.ca> To: chemistry@www.ccl.net Subject: DIAGONALIZATION OF LAGRANGIAN MATRIX Tuesday 1998 Dec 8 Hello, I suspect this question has a simple answer: In one derivation of the Hartree-Fock equations the matrix L of Lagrangian multipliers is written in terms of a diagonal matrix L' L = PL'P**-1 i.e L is diagonalized. This leads to F*psi = e*psi where psi is a column matrix of the, say, electron 1 wavefunctions psi_1(1) psi_2(1) . . . and e (epsilon) is a diagonal matrix (-1/2)l_11 (-1/2)l_22 0 . . 0 . (the Lagrangians turn out to be proportional to the energy levels and books avoid the -1/2 factor, making l_11 = e_1, etc., by slyly putting in a -2, I think, ahead of the game). QUESTION: How do we know that the Lagrangian matrix L is diagonalizable? Is it pretty general that in quantum mechanics square matrices are diagonalizable (that's not the case in mathematics)? Thanks E. Lewars ============ From chemistry-request@server.ccl.net Tue Dec 8 21:35:55 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 VAA04379 for ; Tue, 8 Dec 1998 21:35:55 -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 VAA04717 Tue, 8 Dec 1998 21:30:32 -0500 (EST) Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.7.4/8.7.3) id VAA28456 for chemistry@www.ccl.net; Tue, 8 Dec 1998 21:30:32 -0500 (EST) Date: Tue, 8 Dec 1998 21:30:32 -0500 (EST) From: "E. Lewars" Message-Id: <199812090230.VAA28456@alchemy.chem.utoronto.ca> To: chemistry@www.ccl.net Subject: PAULING POINT--ORIGIN OF TERM 1998 Nov 25 Hello, The term _Pauling point_ is sometimes used for a calculation that gives a good result because errors cancel out--for example, you might get better-than-expected energies or geometries for HF/STO-3G calculations. See for example _Reviews in Computational Chemistry_ Vol. 5, pp. 109, 159. QUESTION: Who originated this term? Is the Pauling Linus Pauling? Thanks E. Lewars ==========================