From moshe_o@VNET.IBM.COM Wed Dec 6 02:56:10 1995 Received: from VNET.IBM.COM for moshe_o@VNET.IBM.COM by www.ccl.net (8.6.10/950822.1) id CAA17547; Wed, 6 Dec 1995 02:52:24 -0500 Message-Id: <199512060752.CAA17547@www.ccl.net> Received: from HAIFASC3 by VNET.IBM.COM (IBM VM SMTP V2R3) with BSMTP id 8856; Wed, 06 Dec 95 02:52:10 EST Date: Wed, 6 Dec 95 09:52:15 IST From: "Moshe Olshansky" To: chemistry@www.ccl.net Subject: combining basis sets - an addition Dear netters! Below is the summary I sent yesterday and for some reason it was not distributed to the list. ========================================================================= Date: 5 December 1995, 13:21:42 IST From: Moshe Olshansky +972-4-296343 moshe_o at vnet.ibm.com To: chemistry at www.ccl.net Subject: combining basis sets - an addition Dear netters! About a week ago I asked the following question: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ P.S. and now I have an additional question: I am a mathematician, not a chemist, so let me look at the basis sets purely mathematically. If one has a complete (and hence necessarily infinite) basis set, he/she gets a limit of Hartree-Fock model. Otherwise (with limited basis set) one gets some approximation to this limit and the more complete the basis set is the better is the approximation. Now assume one uses a certain "standard" basis set and gets some result (from Hartree-Fock model). And now we add ANY additional function to this basis set. This does not make the basis set less complete and so it should lead to at least as good (or even better) an approximation as the original basis did (it is also possible to get the original solution by taking that additional function with zero coefficient for every electron). Is there anything wrong with this statement? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I want to thank all those who replied. As I understand, adding just any function will indeed lower the model energy but the problem is that for unbalanced basis set the wave function with lower energy does necessarily better describe the chemical properties. Below are the responses I received. Moshe Olshansky e-mail: moshe_o@vnet.ibm.com ========================================================================= Date: Tue, 28 Nov 95 10:08:10 -0600 From: smb@smb.chem.niu.edu (Steven Bachrach) Yes, the addition of an extra function MUST result is an energy equal or lower than obtained with the smaller basis set. Having a balanced basis set is only important in two circumstances (1) when you are far from the HF limit (i.e. using a small basis set) and need to get as much of the "correct"soultion as possible (2) when you are trying to do some type of density decomposition in terms of orbital occupancy. Realize that one could describe the LiF molecule with simply a huge number of basis functions centered on just Li. The solution would be identical to one obtained with a large number of orbitals centered on both atoms. Steve Steven Bachrach Department of Chemistry Northern Illinois University DeKalb, Il 60115 Phone: (815)753-6863 smb@smb.chem.niu.edu Fax: (815)753-4802 ========================================================================= Date: Tue, 28 Nov 1995 13:08:57 -0330 (NST) From: Uli Salzner Subject: basis stes Dear Moshe, it is correct that by adding any function to a basis set you get a mathematically improved representation of the wavefunction. The total energy will be lower. The danger is that you might introduce physical or chemical errors by lowering the energy unevenly for the different atoms. The electrons will then flow to the regions where their energy is lower. Try to calculate ethane with an STO-3G basis set on one carbon atom and 6-311+G* on the other carbon and check the charges of both carbons. Mathematically the wavefunction is certainly more complete than with STO-3G on both carbons but the calculation will not reproduce the chemical fact that both carbons are identical. In a geometry optimization not only the distribution of the electrons but also the position of the atoms can be influenced by an unbalance basis set. The reason is that if you use a small basis set, the energy of the molecule gets lower when the atoms are closer together and can use the functions of the neighbor, thus improving their basis sets. This can be due to insufficient basis sets on all atoms or on only one. If you want to see the effect of using different basis sets on a chemical problem, you may look at the results we got for the bond angle of CaF2 with different basis sets: U. Salzner and P. v. R. Schleyer, Chem. Phys. Lett. 1990, 172, p461. Fortunately the problem is normally less severe. CaF2 is an extrem case because the potential energy surface is v e r y flat. Bye, Uli ========================================================================= From: gunnj@CERCA.UMontreal.CA Date: Tue, 28 Nov 1995 12:08:52 -0500 (EST) It depends what you mean by 'better'. What you describe will lower the energy, since that is the function you are variationally minimizing. There is no guarantee that any other function, like the dipole moment for example, will converge 'smoothly' as you add basis functions. Furthermore, the HF approximation is not necessarily very accurate, so approaching that limit might not be what you intuitively expect as an improvement. -- John Gunn (gunnj@cerca.umontreal.ca) | "The world will not be free until Departement de Chimie / CERCA | the last king is strangled with Universite de Montreal | the entrails of the last priest." ========================================================================= Date: Tue, 28 Nov 1995 12:20:15 -0500 From: ryszard@msi.com (Ryszard Czerminski X 217) Dear Moshe, I am not chemist either (I am physicist) so let me say what is my understanding of the concept of "balanced basis set". Your statement that adding "ANY additional function" will make results at least as good is definitely true in the sense that it will produce at least as low total energy as wave function without it. On the other hand this is not always the value you are after. Sometimes you are interested in charge distribution (dipole moments etc...), sometimes in energy differences (when studying molecular complexes). In such cases adding any arbitrary function might make your results worse not better, because these values are not covered by variational principle. This is why, to some extend, generating "well balanced basis set" is sort of "alchemical art" to me. As I understand it, this is the question of compromise between resources (CPU time, memory, etc....) and quality of results for values not necessarily obtained from variational principle (in usual formulation it covers only expected value of the hamiltonian i.e. total energy of the system). With unlimited computational resources the whole idea of well balanced basis sets would be moot. Best regards, Ryszard Czerminski +--------------------------------------------------------------+ | Biosym/Molecular Simulations | phone : (617)229-8875 x 217 | | 16 New England Executive Park, | fax : (617)229-9899 | | Burlington, MA 01803-5297 | e-mail: ryszard@msi.com | +--------------------------------------------------------------+ ========================================================================= Date: Tue, 28 Nov 1995 14:03:26 -0500 (EST) From: "E. Lewars" Hello, This is a comment on your query as to whether increasing the size of a basis set should always improve the calculated results. In practice it does not always give better results (see Warren Hehre, "Practical Methods for Electronic Structure Calculations", Wavefunction Inc., 1995). As a mathematician, you realize we are trying to span an infinite-dimentional vector space with a finite basis set, and it seems that as this set gets bigger the results should get better. However, there is no guarantee that the approach to perfection is smoothly asymptotic; it may oscillate. And in fact a bigger basis set *can* lead to worse results. Best Wishes Errol E. Lewars ========================================================================= Date: Tue, 28 Nov 1995 11:49:18 -0800 From: Rene Fournier Hello ; What you wrote is correct in a sense, but one has to be careful about what is meant by "good" or "better". By virtue of the "variational principle", adding ANY basis function will lower the total Hartree-Fock energy (the energy required to pull to infinity all electrons while keeping the nuclei fixed) and it will get closer to the true total energy. In that sense, results are better. However we are always interested in energy DIFFERENCES, NOT the total energy. Say you underestimate the bond energy of a diatomic AB with a certain basis set and when you add certain functions the energies of A, B, and AB all go down, by 0.1 eV, 0.2 eV, and 0.25 eV respectively. You have better total energies for each of A, B and AB but the dissociation energy is smaller by 0.05 eV and worst than the original one. I think this situation is common with small or medium size basis sets, and not only for dissociation energies but for all properties related to energy differences: ionization potentials, electron affinities, excitation energies, barriers to reaction, harmonic vibrational frequencies, energy differences between conformers, equilibrium geometries. If one judges the quality of results with respect to experiment the issue becomes even more cloudy. If a limit Hartree-Fock calculation overestimates a bond length by 0.10 Angstrom, then using a certain grossly incomplete basis set might bring the Hartree-Fock calculation in perfect agreement with experiment but in error by 0.10 Angstrom from the complete basis set result. Is that good or bad ? It is good in the context of an empirical approach that works systematically, but it is bad if one has an "ab initio" approach. For example, scaled harmonic frequencies calculated by Hartree-Fock with some small basis are "good" from an empirical point of view. My overall impression from the quantum chemistry literature is this. When using a small or medium basis set, adding basis functions can worsen energy differences almost as likely as they can improve it, unless one uses "chemical intuition" to choose precisely what basis functions to add. When using very large basis sets, I think that adding more basis functions almost always improves all results (or leaves them unchanged). Here is a humoristic illustration of this. This graph pretends to show the error on a typical property measured relative to experiment as a function of the level of theory and the "3 zero-error regions" where quantum chemists try to work: "Pauling's", "HF/6-31G" (or today we might say "BLYP//6-31G" ?!), and the "really good calculation". A similar graph may apply also if the x-axis was labeled "basis set size" and the graph referred only to Hartree-Fock calculations with error measured relative to limit Hartree-Fock. ( Note: I made this graph from memory from a similar one I saw in a lecture by P. O. Lowdin; my apologies for possible inacurracies or misrepresentation. I think it was a very good graph! ) ^ | | | x x E |x r |x r |x o |x r | x | x | x | x Really, REALLY tough | x x x / fully ab initio | x Pauling's level x x / calculation | x of theory x x / | x / x x | x / x |---> x | x / x |---> x 0| |x | | x | | x ----|---|-x-|-------|--x--|------------------|-----------------------x---> |0 | x | | x | | Level of theory; | x x \ Computational effort | x x \ | x x \ | x x Hartree-Fock 6-31G | level of theory Sincerely, Rene Fournier. |-------------------------------|-----------------------------| | Rene Fournier | fournier@physics.unlv.edu | | Department of Physics | fournie@ned1.sims.nrc.ca | | University of Nevada | phone : (702) 895 1706 | | Las Vegas, NV 89154-4002 USA | FAX : (702) 895 0804 | |-------------------------------|-----------------------------| ========================================================================= Georg Schreckenbach Tel: (Canada)-403-220 8204 Department of Chemistry FAX: (Canada)-403-289 9488 University of Calgary Email: schrecke@zinc.chem.ucalgary.ca 2500 University Drive N.W., Calgary, Alberta, Canada, T2N 1N4 ============================================================================== From: "Victor M. Rosas Garcia" Date: Tue, 28 Nov 1995 23:02:46 -0500 I'm a chemist, not a mathematician, but I like this kind of problems so, here I go: I'd say, yes, there is something wrong with the statement. First I want to point out what I consider is a small contradiction in your argument, first you say: "let me look at the basis sets purely mathematically" which I understand as dismissing any considerations of "physical meaning". Then you say: "If one has a complete (and hence necessarily infinite) basis set, he/she gets a limit of Hartree-Fock model." Now we are considering the basis sets within the frame of a physical model (the Hartree-Fock approximation) and therefore we are not considering them purely mathematically. Having said that, my reasoning is as follows: Inasmuch as the basis set complies to certain requirements of the physical model (e.g. a functional form that will "imitate" Slater Type Orbitals), the addition of ANY function (which in the general case does not comply to those requirements) will affect negatively the result of the calculation. I mean, as far as the Hartree-Fock model is concerned. just my $0.02 Victor -- ----------------------------------------------------------------------- Victor M. Rosas Garcia * "How can we contrive to be rosas@irisdav.chem.vt.edu * at once astonished at the Virginia Tech doesn't necessarily share * world and yet at home in it?" the opinions you just read. * G. K. Chesterton ------------------------------------------------------------------------- ========================================================================= Date: Wed, 29 Nov 1995 11:10:00 +0100 From: peon@medchem.dfh.dk (Per-Ola Norrby) It of course depends on what you mean with "better". The SCF will minimize the energy, adding any new function should give an energy closer to the HF limit. However, most of the time this is not really interesting. When you want energies, you usually want relative energies, and then it's quite important that you make the same approximations, that is, calculate at a constant level of theory, so that systematic errors cancel. Also, as you said in the part of the message I deleted, adding functions in an unbalanced way will definitely affect the charge distribution, probably not making it "better" :-) Specific questions can sometimes be answered by including functions that are not atom-centered, but then you get the problem of findning a completely reproducable way of doing that for any system. Per-Ola Norrby ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ --- Bureaucracy is a challenge to be conquered with a righteous attitude, a tolerance for stupidity, and a bulldozer when necessary -- Peter's Law 15. * Per-Ola Norrby * The Royal Danish School of Pharmacy, Dept. of Med. Chem. * Universitetsparken 2, DK 2100 Copenhagen, Denmark * tel. +45-35376777-506, +45-35370850 fax +45-35372209 * Internet: peon@medchem.dfh.dk, peo@compchem.dfh.dk ========================================================================= Date: Wed, 29 Nov 1995 13:25:18 +0100 (NFT) From: oppel@pctc.chemie.uni-erlangen.de Dear Moshe, concerning your question about adding any basis-function to an existing basis-set, I think you are right in principle, that this function doesn't make the basis worse, i.e., the energie becomes 'better' in the sense, that it reaches the exact solution. BUT, often the energy is not the quantity a chemist is interested in. Especially, if one takes a look at the charges at a certain atom in a system, one uses the so-called Mulliken-analysis (as you may know), to get this information. Unfortunatly, this quantity isn't even an obsevable, so one cannot get it be taking the expectation-value of an hermitian operator. One takes the difference between the nuclear charge at the atom and the sum of the diagonal-elements of P*S, which belong to this atom. Now, if you have an unbalanced basis-set, you will get charges which are far from reality. In the worst case, think of a complete basis, where all the functions are centered on a single atom. If you do now a Mulliken-analysis, you will find no electrons on the other atoms, though the solution of the HF-equations is exact. So, take care of your basis-set, and choose it well for the chemical problem you have to solve. Markus Oppel Chair for theoretical chemistry University of Erlangen-Nuernberg Germany oppel@pctc.chemie.uni-erlangen.de From chem@oxygen.chem.nthu.edu.tw Wed Dec 6 03:41:11 1995 Received: from nthu.edu.tw for chem@oxygen.chem.nthu.edu.tw by www.ccl.net (8.6.10/950822.1) id DAA18054; Wed, 6 Dec 1995 03:33:23 -0500 Received: from oxygen.chem.nthu.edu.tw ([140.114.45.223]) by nthu.edu.tw with SMTP id <181981(1)>; Wed, 6 Dec 1995 16:41:52 +0800 Received: by oxygen.chem.nthu.edu.tw (th3.3w) id AA01748; Wed, 6 Dec 95 16:22:27 +0800 From: chem@oxygen.chem.nthu.edu.tw Subject: Postdoc Position in Biophysics To: chemistry@www.ccl.net Date: Wed, 6 Dec 1995 16:22:27 +0800 X-Mailer: ELM [version 2.4 PL23] Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Content-Length: 3461 Message-Id: <95Dec6.164152cst.181981(1)@nthu.edu.tw> I am seeking post-doctoral candidates to work on biological structure, dynamics and function and thus have: (i) solid training in biophysics; i.e., quantum mechanics, statistical mechanics as well as general biochemistry and biophysical methods, and (ii) experience in applying molecular dynamics (like CHARMM) and Monte-Carlo techniques. Candidates should have a Ph.D. in Physics, Chemistry, Biophysics, or related areas and preferably have the background stated above as well as have no visa problems entering Taiwan. Further enquiries and applications (resume and names of 3 references) should be sent to: Carmay Lim E-mail: carmay@ibms.sinica.edu.tw Institute of Biomedical Sciences, Off: 011-886-2-789-9144 Academia Sinica, FAX: 011-886-2-785-3569 Taipei, Taiwan 11529 NB. 011 is for international dialing (may differ outside U.S.), 886 is the country code (Taiwan), and 2 is the city code (Taipei). The Institute of Biomedical Sciences (IBMS), Academia Sinica. ************************************************************* The set-up is more akin to that at the National Institutes of Health, rather than at a University in the U.S. or Canada. One of the aims of IBMS is to provide a favorable research climate and in-depth training of scientists interested in biomedical sciences. Our computational biophysics group is part of the Structural Biology program which also includes protein and peptide design, NMR, MRI (Magnetic Resonance Imaging), X-ray, and optical spectroscopy. Funding ******* The post-doctoral fellow salary is set at the National Science Council scale of NT$48,000/month + 1.5 year end bonus. (1 NT$ = 0.053 Canadian dollar). The salary will initially be provided by IBMS but you can also apply for a post-doctoral fellowship from the National Science Council (NSC) as well as Academia Sinica (AS) . In the latter, there are 3 categories: I. Academia Sinica pd fellow - awarded to only top 10% - higher than NSC salary but - the exact amount is awarded on a point basis II. pd fellow - NSC salary scale III. Senior pd fellow - those with at least 4 years of - pd experience Appointment usually lasts for 2 years per term, renewable for another term. Note that you will only have to pay 8 to 10% tax and Academia Sinica will provide comprehensive health coverage for you and immediate family members. Computing environment ********************* Apart from our own facilities (IBM 590, SGI POWER INDIGO R8000, POWER CHALLENGER M R8000), we have free access to supercomputers and workstations at the National High Speed Computing Center and Academia Sinica Computing Center (for further information, check gopher or www). Labarotory Space **************** We will occupy the entire floor of a new building. Living expenses *************** You may stay at the Activity Center (which is a 3--5 minutes walk from IBMS) for NTD$15,000/month - this includes room service. You may of course choose to rent: post-docs have recently rented a single room (~150 sq. ft) for NTD$4,000/month and a 3-bedroom apartment (~800 sq. ft) for NTD$11,000/month. For meals at the activity center, lunch costs ~NT$50 and dinner costs ~NT$100-250. The bus fare is around NT$10-20 (depending on the distance) and the cab fare is NT$50 + NT$5 for each additional 1/4 km. From smori@chem.s.u-tokyo.ac.jp Wed Dec 6 23:56:25 1995 Received: from utsc.s.u-tokyo.ac.jp for smori@chem.s.u-tokyo.ac.jp by www.ccl.net (8.6.10/950822.1) id XAA04168; Wed, 6 Dec 1995 23:42:05 -0500 Received: from [133.11.6.112] (smori.chem.s.u-tokyo.ac.jp) by utsc.s.u-tokyo.ac.jp (5.67+1.6W/TISN-1.3/R2) id AA01342; Thu, 7 Dec 95 13:41:43 JST Message-Id: <9512070441.AA01342@utsc.s.u-tokyo.ac.jp> Date: Thu, 7 Dec 1995 13:46:11 +0900 To: chemistry@www.ccl.net From: smori@chem.s.u-tokyo.ac.jp (Mori Seiji) X-Sender: smori@chem.s.u-tokyo.ac.jp (Unverified) Subject: Summary of NMR calculaton. Cc: smori@utsc.s.u-tokyo.ac.jp Mime-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp X-Mailer: Eudora-J(1.3.8.5-J13) Dear netters, Thank you for several replies about my questions for the method of NMR chemical shift, and so on. Replies about isotropy and anitrosopy which I posted will be sent soon. I think the reliability of IGAIM , CSGT in G94 packages were not known very much thus we have to check these methods comparing with known methods. The systematic review of solvent effects, polarity and coordination with donating solvent such as ether have still be awaited. Sincerely yours, Seiji Mori ---my original question--- Dear everybody, Recently, many letters about NMR chemical shift calculation were posted, and I am also interested in NMR shifts in organic and organometallic complexes in solution. I have several questions, 1. How is the reliablities of 1.1 methods (GIAO, IGAIM, CSGT, IGLO) 1.2 theory (HF,DFT,MP2...CC) and basis-sets 1.3 How is the solvent effect of polarity on the NMR shift, coupling constant (I think it is not related calcluation , probably it is a fundamental question about NMR)? 2. Do you know the program or references which one can calculate not only chemical shift but also the coupling constant ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than G94? As to 1H-1H coupling constant, many programs such as PCMODEL was supported but its calculation is not QC. If you have comments and indicate the references, would you please send me ? I will summarize replies. Thanks in advance, Seiji Mori ------------- Replies ---1--- Received: by zinc.chem.ucalgary.ca (AIX 3.2/UCB 5.64/4.03) id AA10813; Fri, 24 Nov 1995 15:29:30 -0700 From: schrecke@zinc.chem.ucalgary.ca Message-Id: <9511242229.AA10813@zinc.chem.ucalgary.ca> Subject: Re: CCL:NMR shift and coupling constant calculation Hi Seiji, you have quite a lot of questions in your posting ... I shall try to give you a few hints, with no intention to be comprehensive. > > 1. How is the reliablities of > 1.1 methods (GIAO, IGAIM, CSGT, IGLO) > 1.2 theory (HF,DFT,MP2...CC) and basis-sets > 1.3 How is the solvent effect of polarity on the NMR shift, coupling > constant > (I think it is not related calcluation , probably it is a fundamental > question about NMR)? Good references to start with are three nice reviews, one new, two are older: D.B.Chesnut: Annual Reports on NMR Spectroscopy, published by Academic Press, Vol.21,1989, p. 51 and ibid, Vol. 29, 1994, p.71. H.Fukui: Magn. Res. Rev. 1987, vol. 11, 205 Further, very comprehensive reviews are contained in an annual series, since 1980 written every year by C.Jameson: in Specialist Periodical Report on Nuclear Magnetic Resonance, Vol.8,1980-... (edited by G.A.Webb, and published by the Royal Society of Chemistry, Cambridge) Now more specific comments on your various questions. 1.1 Methods with distributed gauge origins (IGLO, LORG, GIAO,...) are generally preferable (for a given basis set) over methods with a common gauge origin. For examples, see the various reviews. GIAO seems to converge slightly faster with the size of the basis set then IGLO (see Wolinski, Hinton, Pulay, JACS 1990, 112, 8251). This would also make sense from a theoretical point of view. I don't know off hand about IGAIM, CSGT. 1.2 Correlation. there are cases where correlation is necessary, e.g., M.Buehl et al. J.Phys.Chem. 99, 4000 (1995), and M.Buehl et al. Chem.Phys.Lett. 241 (1995), 248. These papers contain examples where MP2 fails completely to predict the shift while DFT and CCSD are able to achieve quantitative results. There are however many other cases where the HF level works just fine (all the respective literature up to -- say -- five years ago). Basis sets. See about any paper with calculated shifts. E.g., the one by Pulay et al. mentioned above, or various papers by the Kutzelnigg group, or the various reviews. 1.3 Solvation effects can be considerable, indeed. Look for experiments that were done in the gas phase (in addition to solution studies). A review of gas phase NMR was written by C. Jameson: Chem.Rev.1991, 91, 1375. > 2. Do you know the program or references which one can calculate not only > chemical shift but also > the coupling constant > ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than > G94? As to 1H-1H > coupling constant, > many programs such as PCMODEL was supported but its calculation is not QC. Coupling constants are MUCH tougher to calculate than chemical shifts. The reason is (in my opinion) that you are dealing with operators that evaluate the electron density in essentially just one point of space rather than over an entire region of space. Annual reviews of calculations are contained in the same series of books that was metioned before: Specialist Periodical Report on Nuclear Magnetic Resonance Calculations have been done recently, e.g., by Erikson/Malkin/Salahub et al. but I don't have the references on hand right now. I am looking forward to your summary! Yours, Georg ============================================================================== Georg Schreckenbach Tel: (Canada)-403-220 8204 Department of Chemistry FAX: (Canada)-403-289 9488 University of Calgary Email: schrecke@zinc.chem.ucalgary.ca 2500 University Drive N.W., Calgary, Alberta, Canada, T2N 1N4 ============================================================================== ---2--- From: "Steve Gwaltney" Received: by red11 (SMI-8.6/4.11) id KAA08969; Mon, 27 Nov 1995 10:51:20 -0500 Date: Mon, 27 Nov 1995 10:51:20 -0500 > 2. Do you know the program or references which one can calculate not only > chemical shift but also > the coupling constant > ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than > G94? As to 1H-1H ACES II can calculate chemical shifts using GIAO's and MBPT(2) wavefunctions. ACES II can also calculate CCSD coupling constants. For information about ACES II contact aces2@qtp.ufl.edu. I believe TURBOMOLE can also calculate chemical shifts, but you should check with them to make sure. Steve Steven Gwaltney gwaltney@qtp.ufl.edu Quantum Theory Project University of Florida ---3--- From: wagenert@Mailer.Uni-Marburg.DE (Wagener Thomas) Subject: CCL:NMR shift and coupling constant calculation Date: Mon, 27 Nov 1995 14:12:47 +0100 (CET) Dear Seiji Mori, since I have finished my thesis on the ab-initio calculation a few month ago, I hopefully can help you with some of your questions. > 1. How is the reliablities of > 1.1 methods (GIAO, IGAIM, CSGT, IGLO) > 1.2 theory (HF,DFT,MP2...CC) and basis-sets > 1.3 How is the solvent effect of polarity on the NMR shift, coupling > constant I had only the opportunity to work with GIAO and IGLO so I can only make a statement on these methods. Basically IGLO and GIAO are quite reliable for the calculation of "standard" organic compounds though the accuracy of the methods is not as high as the experimental accuracy. A rough estimate would be an accuracy of about 5ppm for 13C chemical shifts - probably better. Taking into account that you are comparing gas phase values at absolute zero with values taken from a sample in solution at a temperature of, say, 200-300K that is probably as close as you can get. The computational effort for the IGLO method is somewhat higher than for the GIAO calculation (at HF-level) though the information you get from IGLO is more extensive. Because IGLO works with localized molecular orbitals (LMOs) you get an anlysis of the contribution of the LMOs to the chemical shift while you only get the shielding constant out of the GIAO calculation. IGLO is available at HF level and there is a DFT version using the IGLO code to calculate chemical shifts. The GIAO method in MO theory is available up to CC level though the computational effort is extremely high so the calculation of the shielding constant at such a highly coorelated level is only possible for small molecules. The GAUSSIAN94 manual states that the GIAO module of the program can cope with DFT but I have no experience with that. > 2. Do you know the program or references which one can calculate not only > chemical shift but also > the coupling constant > ( for example, 1H-1H and 13C-13C) and NOE in quantum chemistry other than > G94? As to 1H-1H coupling constant, As far as I know (and I really may not be up to date) the only programs capable of calculating coupling constants is DeMon with DFT-IGLO and ACESII (at MP2 level). Some useful references are: - IGLO: Kutzelnigg, W.; Fleischer, U.; Schindler, M.:"The IGLO-Method: Ab- initio Calculation and Interpretation of NMR chemical Shifts and magnetic Susceptibilities", NMR Basic Princ. Prog., Vol. 23, Springer-Verlag, Berlin Heidelberg, 1990, 165 - DFT-IGLO: Malkin, M. G.; Malkina, O. L.; Casida, M. E.; Salahub, D. R., JACS, 116(1994), 5898 - HF-GIAO: Wolinski, K.; Hilton, J. F.; Pulay, P., JACS, 112(1990), 8251 - MP2-GIAO: Gauss, J., Chem. Phys. Lett., 191(1992), 614 Hope, this was of some help Thomas Wagener - "You are wrong! 2+2=5.8354! Please adjust your equipment accordingly." The Computer (your friend) ***************************************************************************** * Thomas Wagener * Tel: ++49-(0)6421-285561 * * FB Chemie * * * Phillips-Universitaet Marburg * Email: wagenert@mailer.uni-marburg.de * * * * * 35032 Marburg * * * Germany * * ***************************************************************************** ---end -- #################################################### Seiji Mori Graduate student in Nakamura Laboratory Department of Chemistry The University of Tokyo Hongo 7-3-1, Bunkyou-ku, Tokyo 113, JAPAN. email:smori@chem.s.u-tokyo.ac.jp ####################################################