From qnetua!qnet.odessa.ua!kruglyak@iron.tenet.odessa.ua Sun Jan 14 06:03:46 1996 Received: from relay5.UU.NET for qnetua!qnet.odessa.ua!kruglyak@iron.tenet.odessa.ua by www.ccl.net (8.6.10/950822.1) id FAA18590; Sun, 14 Jan 1996 05:55:15 -0500 Received: from nipple.TeNeT.Odessa.UA by relay5.UU.NET with ESMTP id QQzylv08616; Sun, 14 Jan 1996 05:54:59 -0500 (EST) Received: from ignet.ignet.odessa.ua (root@tenet.ignet.odessa.ua [194.44.73.200]) by nipple.TeNeT.Odessa.UA (8.6.12/8.6.9) with ESMTP id LAA11900 for ; Sun, 14 Jan 1996 11:19:00 +0200 Received: (from uuqnet@localhost) by ignet.ignet.odessa.ua (8.6.9/8.6.9) id LAA02118 for chemistry@www.ccl.net; Sun, 14 Jan 1996 11:15:35 +0200 Received: by ignet.ignet.odessa.ua (uumail v1.5/ache) with UUCP id AA02107; Sun, 14 Jan 1996 11:15:33 +0200 Received: by qnet.odessa.ua (dMail for DOS v1.23, 15Jun94); Sun, 14 Jan 1996 11:18:37 +0200 To: chemistry@www.ccl.net Message-Id: Organization: QuantumNet Date: Sun, 14 Jan 1996 11:18:37 +0200 (EET) Return-Receipt-To: kruglyak@qnet.odessa.ua From: "Yurii Kruglyak" X-Mailer: dMail [Demos Mail for DOS v1.23] Subject: To Those CCL Members Who are Conserned Lines: 70 PARTNERSHIP WANTED FSU Members of the Public Association "QuantumNet" are looking for research co-operation along the following projects-on-line and, in particular, for U.S.Co-Investigators to submit together joint projects to Cooperative Grants Program of U.S. Civilian Research and Development Foundation for the Independent States of the FSU/CRDF E-mail: information@crdf.org Fax: 703/526 9721 Tel: 703/526 9720 Details of the Projects are available on request. Point of Contact: kruglyak@qnet.odessa.ua FaxLine: +380(482)63 77 85 Voice : +380(482)60 33 14 January 17, 1996 PUBLIC ASSOCIATION QuantumNet gopher://www.ccl.net:73/00/info/societies/Quantum-Net ------------------------------------------------------------------------------ QNet1: 1.1: Photocatalysis on Dispersed Titanium Dioxide Surface: QuantumChemical Study ----------------------------------------------------------------------- 1.2: Computer Simulation of Alkali Metal Ions Sorption on Silicate and Alumosilicate (Dr. Victor V.Lobanov, Kiev) ------------------------------------------------------------------------------ QNet2: Gas-Phase Spontaneous and E-Field Induced Rearrangements of Neutrals C6H5-R (R = CH2, NH, O, S) and Their Charged Ions: QuantumChemical Study ----------------------------------------------------------------------- QNet3: Fully Weighted Molecular Graph Invariants Approach with Application to Structure - Critical Properties Quantitative Predictions: Alkanes, Freons, and their Si- and Ge-Analogues (Prof. Yurii A.Kruglyak, Odessa) ------------------------------------------------------------------------------ QNet4: 4.1: 3D QSAR Modelling Based on New Lattice Parameters of Molecular Structure and Neuronet Algorithms ----------------------------------------------------------------------- 4.2: Studies of 3D Structure of Molecules with the Use of Combinatorial Topology (Dr. Victor E.Kuz'min) ------------------------------------------------------------------------------ QNet5: Catalysis of Diatomics on Metals, Metallic Alloys, and Semiconductors: Electrodynamical & QuantumChem.Modelling(Prof.Aleksandr Glushkov,Odessa) ------------------------------------------------------------------------------ QNet6: Lattice-topological Modelling of Molecules as a Source of Parameters for Structure - Properties Problems ----------------------------------------------------------------------- QNet7: Fractal Approach for Molecular Structure Modelling ----------------------------------------------------------------------- QNet8: New Conception of Stereochemical Configuration and New Approaches for Quantitative Estimation of Chirality ----------------------------------------------------------------------- QNet9: New Molecular Shape Parameters for Analysis of Steric Key-Lock Type Correspondance: Molecular Design Technology of SupraMolecular Complexes (Dr. Victor E. Kuz'min, Odessa) ------------------------------------------------------------------------------ QNet10: Intellectual Modelling and Knowledge Presentation for Thermodynamics and Quantum Chemistry Applications (Prof. Victor A. Mazur, Odessa) ------------------------------------------------------------------------------ QNet11: Antropogenic Influence on the Environment of the Black Sea, the Dniester River, the Danube River and the Yuzhniy Bug River: Social Ecology Aspects ---------------------------------------------------------------------- QNet12: Estimation of the Danger Level of Harmful Objects of the Coastal Zones [Ports, Terminals, Ship-Building and Ship-Repair Yards, Storages of Harmful Substances and Materials etc]: Social Ecology Aspects ---------------------------------------------------------------------- QNet13: Ecological Education: 13.1: Program of the Pre-School Ecological Education 13.2: Ecological Cources for School Children and Students 13.3: Preparation and Usage of Ecological Games, Tales, and Stories 13.4: School-chidren and Students International Conference on Ecology and Environment Protection ---------------------------------------------------------------------- QNet14: Editorial Projects in Ecology, Education, and Culture: 14.1: Publishing the Ukrainian-Russian-English Dictionary on the Ecology and Environment Protection 14.2: Edition of a New Quarterly Magazine "Accidents, Disasters, and Civil Defense": Ecological and Industrial Accidents and Catastrophes//Experience, Prevention, and Liquidation of Consequences 14.3: Publishing of Educational Materials ---------------------------------------------------------------------- QNet15: Research in Ecology: 15.1: Determination of the Ecological Risk Factors for the Regions of Ukraine, in particular, for Odessa Region ---------------------------------------------------------------------- 15.2: Modelling, Prediction, Preventation, and Liquidation of the Ecological Catastrophes in the Coastal Zones ---------------------------------------------------------------------- 15.3: Mineral Waters, Salts, Health Resort and Medical Resources of the Northern-Western Black-Sea Region ---------------------------------------------------------------------- 15.4: New Fuel and Voltaic Cells as the Basis of the Alternative, Safe-Ecological Technologies (Prof. Alfred L.Tsykalo, Odessa) ------------------------------------------------------------------------------ QNet16: 16.1: The Influence of Magnetic and Electric Fields on Electron-Hole Pair PhotoGeneration in Polymeric PhotoSemiconductors ---------------------------------------------------------------------- 16.2: Development of Holographic Recording Media for Interferometry of Low-Contrast Objects ---------------------------------------------------------------------- 16.3: Transport of Unsteady Current Carriers in the Films of Amorphous Molecular Semiconductors (Prof. Nikolai G.Kuvshinsky, Kiev) ------------------------------------------------------------------------------ QNet17: 17.1: Mathematical Study of the Stability Problem of the Stationary Flow of Fluids with the Variable Physical Properties ---------------------------------------------------------------------- 17.2: Splintering Kinetics of Drops in High-Speed Gas Flow and Theory of Detonation of Liquid Aerosols (Prof. Sergey K.Aslanov) ------------------------------------------------------------------------------ QNet18: Organic Synthesis and Physical Organic Chemistry of Acenaphthene, Acenaphthylene, Naphthalic Anhydride, Naphthalimide Derivatives and Related Compounds (Prof. Valery F. Anikin, Odessa) ------------------------------------------------------------------------------ QNet19: 19.1: Structure and Energetics of Ions Clusters in Metallic Hydrogen ---------------------------------------------------------------------- 19.2: Thermodynamic Properties of Amorphous Magnets with Ferro- and Antiferromagnetic Bonds ---------------------------------------------------------------------- 19.3: Microscopic Theory of the Surface Structure of Disordered Metalls (Prof. Nikolay P. Kovalenko, Odessa) ------------------------------------------------------------------------------ QNet20: 20.1: Modelling the RedOx Enzymes by the Porphyrin Structures: Physico-Chemical Basis, Studies in vitro ---------------------------------------------------------------------- 20.2: Modelling the Chlorophyll-like Compounds on the Basis of the Meso-Substituted Porphyrins ---------------------------------------------------------------------- 20.3: New Aspects of Functionalization of the Porphyrin Ring in the Mesotetraphenylporphyrine ---------------------------------------------------------------------- 20.4: Vicarious Nucleophylic Substitution of Hydrogen in the Tetraarylporphyrins (Prof. Z.I.Zhilina) ------------------------------------------------------------------------------ From young@argus.cem.msu.edu Sun Jan 14 20:18:46 1996 Received: from argus.cem.msu.edu for young@argus.cem.msu.edu by www.ccl.net (8.6.10/950822.1) id UAA23120; Sun, 14 Jan 1996 20:09:40 -0500 From: Received: from slater.cem.msu.edu by argus.cem.msu.edu via ESMTP (950215.SGI.8.6.10/940406.SGI) for id UAA24601; Sun, 14 Jan 1996 20:10:09 -0500 Received: by slater.cem.msu.edu (950215.SGI.8.6.10/) for chemistry@www.ccl.net id UAA25648; Sun, 14 Jan 1996 20:10:36 -0500 Date: Sun, 14 Jan 1996 20:10:36 -0500 Message-Id: <199601150110.UAA25648@slater.cem.msu.edu> To: chemistry@www.ccl.net Subject: RE:search mathematical theorems I submitted this message a few days ago, but it seems to have evaporated, possibly due to our computer technician restructuring mail. My apologies if this is a duplicate for you. Peter Huesser wrote > > Dear Netters: > >Does anybody know if there are some mathematical investigations >in which cases the self consistent procedure finds a minimum ? >What I mean is the following: do there exist some theorems >which allow to decide for which starting hamilton and >configuration a minimum is found ? >I am looking for books or papers. This is part of the branch of mathematics known as "Chaos Theory" It is the mathematics of itterative procedures in which the input to an itteration is the output of the previous itteration. Chaos and Fractal Geometry are two sides of the same piece of mathematics. What Chaos theory says is that a self consistent procedure can do one of the following. 1. Converge to a stable solution. 2. Sit on an unstable solution (maxima) only if the exact maxima was used for the initial guess. 3. Oscillate between 2**N (2, 4, 8, 16, etc) different values on successive itterations. 4. Give chaotic (random) values within some upper and lower bounds on successive itterations (and never converge). 5. Give chaotic values which are unbounded. I have seen examples of all of these in HF and MCSCF calculations. Open shelled transition metal calculations are particularily prone to oscillating and chaotic SCF convergence due to the presence of many low lying exited states, so the solution may be getting a piece of nearby states and trying to converge to two places at once (no rigorous proof, but thinking of it this way will lead you to the correct procedure for correcting the problem). Which of the above behaviors is observed is dependent upon the initial guess, the equations being used and the constants in the equations. This is why the fix for a calculation that isn't converging is to try a different initial guess, use level shifting, or switch from DIIS to a quadraticly converging method. A very useful technique that is often overlooked is to use a program which uses a block diagonal form of the hamiltonian and allows you to specify how many electrons are of each irreducible representation. This prevents oscillation between states of different wave function symmetry. Just a side note, quadratic convergent methods are extremely slow and often an act of sheer desperation. We usually find the most efficient way to do open shell transition metals is to construct the first guess by hand then use previous calculations as guesses. Anyway, back to the original question. It has been a couple years since I looked through this branch of mathematics, but the last time I did the mathematicians were having pretty good success at predicting what conditions would lead to each of the five possible convergence behaviors. The more fundamental question of why it is this way was still a matter of hot debate last time I looked. I am not aware of anyone yet applying these techniques to MO SCF procedures. If anyone knows of such, please send me a reference or post it to the list. Hope this helps. Dave Young young@slater.cem.msu.edu -------------------------------------------------------------------------- When all else has been ruled out as impossible, what ever remains, however improbable, must be the truth. words of Sherlock Holmes Arthur Conan Doyle -------------------------------------------------------------------------- From /G=Matthew/S=Harbowy/OU=LIPTONUS-EC02/O=TMUS.TJL/@LANGATE.gb.sprint.com Fri Jan 12 15:34:46 1996 Received: from merit-mx1.telemail.net for /G=Matthew/S=Harbowy/OU=LIPTONUS-EC02/O=TMUS.TJL/@LANGATE.gb.sprint.com by www.ccl.net (8.6.10/950822.1) id PAA06337; Fri, 12 Jan 1996 15:34:38 -0500 From: Date: Fri, 12 Jan 1996 13:32:00 -0500 X400-Originator: /G=Matthew/S=Harbowy/OU=LIPTONUS-EC02/O=TMUS.TJL/@LANGATE.gb.sprint.com Content-Identifier: Re: CCL:Chiral S Message-ID: <"Fri Jan 12 13:32:00 199601*/G=Matthew/S=Harbowy/OU=LIPTONUS-EC02/O=TMUS.TJL/PRMD=LANGATE/ADMD=TELEMAIL/C=GB/"@MHS> To: hyperchem@hyper.com Cc: chemistry@www.ccl.net Subject: Re: CCL:Chiral Selectivity -Reply >One of the problems to be aware of is that in real life there will not >be 100 % enantioselectivity. Hence there are probably two pathways to >product, one going through a higher energy pathway than the other, >which corresponds to the chiral selectivity observed. This real energy >difference only has to be small to give large enantiomeric excesses. >Unfortunately, I feel the accuracy of the calculations involved can be >less than the accuracy required. The good minimisers available today >would prefer to seek out this global minimum - corresponding to the ^^^^^^^^^^^^^^ >product in excess, and hide the pathway that gives the other >enantiomer - hence hiding valuable information. The vast majority of minimization algorithms *do not* see global minima, but the *nearest* minimum. While small differences in energy do represent large differences in enantioselectivity, this says nothing about the potential energy surface and two 'minima' can have drastically different geometies and can be separated by fairly large energy barriers, allowing good discernment between minima. In addition, it should be noted that enantioselective catalysts may result in different geometries/energies for the transition state of one isomer or the other, so doing an 'optimization' of a 'minimum' is not always the desired calculation. True differences in product distributions should only be measurable by dynamic modeling of an ensemble of conformations. One should be able to minimize to both enantiomers (which should be exactly the same energy in vacuo/in the absence of other molecules). One should be able to minimize a catalyst. But the tacking of substrate onto catalyst requires good intermolecular paramaters, and a simple 'minimization' will probably see hunderds of local minima, depending on orientation. It is less that you hide the unfafored enantiomer, but that you have no idea whether you're at the 'true' preferred conformers for either favored *or* unfavored. In short, such modelling is clearly beyond the limited capabilities of Hyperchem at the present time. >My advice is therefore to try and explain things in terms of steric >hindrance to explain the observed chiral selectivity, and apply a little >chemical intuition before trusting the numbers generated. Try to think of >how the enantiodifferentiation could occur, and place the reactant in a >relavant orientation wrt to the chiral adduct and then perform a >minimisation. Do this for both enantiomers. Not an ideal situation I know >but it may help. At that point, you have to ask, why are you doing computer modeling? If you are using a massively qualitative model, why go through the expense of extended computation if you can make good 'guesses' with chemical intuition? At some point, it seems that one is using 'modeling' to generate good 'visualizations' and not much 'data'. That seems like a fine use of hyperchem, to easily generate 3-d models for visualization, but it would seem that any computation one does will be heavily biased by the model. All assumptions should be designed to be falsifiable: that is, you can say the opposite, and prove it is untrue. Additionally, what parameters do you use? Molecular Mechanics? At some point, you'll need to create a new parameter specific to your model, one which you can 'fudge' but have a good justification for doing so. Then minimizations can occur; but with 'standard' parameters, I'm not sure how well intermolecular and electronic effects are reproduced. matt