From chemistry-request@server.ccl.net Mon May 22 01:57:04 2000 Received: from nmr-v.ioc.ac.ru (root@nmr-v.ioc.ac.ru [193.233.3.213]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id BAA08289 for ; Mon, 22 May 2000 01:57:03 -0400 Received: from cacr.ioc.ac.ru (val@localhost [127.0.0.1]) by nmr-v.ioc.ac.ru (8.9.3/8.9.3) with ESMTP id JAA03415 for ; Mon, 22 May 2000 09:56:51 +0400 Sender: val@nmr-v.ioc.ac.ru Message-ID: <3928CC21.BE2BF64E@cacr.ioc.ac.ru> Date: Mon, 22 May 2000 09:56:49 +0400 From: Valentine Ananikov Reply-To: val@cacr.ioc.ac.ru Organization: IOC X-Mailer: Mozilla 4.7 [en] (X11; I; Linux 2.2.13 i686) X-Accept-Language: ru, en MIME-Version: 1.0 To: CCL_post Subject: Re-REPLY: CCL:1,3,5-cyclohexatriene References: <39285C3B.2D92209C@trentu.ca> Content-Type: text/plain; charset=koi8-r Content-Transfer-Encoding: 7bit Hello, Not all of the possible 1,3,5-cyclohexatriene isomers could be assumed as a resonance structures, neither the vibrational extremes. For example, cis,cis,trans-1,3,5-cyclohexatriene, so called "Mobius benzene", does not seem to fit into the resonance structures active space. It may be converted to classical planar forms through the trans/cis isomerization, however this implies some activation barrier. The comments below concerning the resonance hybrid and real existence of a compound are qualitatively correct. Perhaps, somebody may formulate the quantitative rules also? best regards, Valentin. > > 2000 mAY 21 > > Hello, > > The answer to your question (below), phrased as a general problem, is > not as quite simple as one may think. The conventional response would be > that cyclohexatrine structures are resonance structures (canonical > structures) contributing to the actual structure, a resonance hybrid, > and so can't have any real existence: they are just bond-stretching > vibrational extremes with benzene vibrating about a geometry of mean > (average) hexagonal symmetry (think of a Morse curve). the energy of the > purely hypothetical 1,3,5-cyclohexatriene has been evaluted in > connection with its use as areference molecule in assigning a resonance > energy to benzene (e.g. work by M. J. S. Dewar--treated in some org chem > textbooks). > > So much for benzene, but for cyclobutadiene the alternating C-C/C=C > structures are real: the potential energy surface has two minima > separated by a transition state. Predicting the results for simple > polyene cases requires, usually, only knowing about aromaticity and > antiaromaticity and the Hueckel rule, but _generally_ distinguishing > between resonance (as in benzene) and valence tautomerism (as in > cyclobutadiene) requires actual calculation. The problem of "the thin > line" (quoting Paquette) between the two was discussedby L. Paquette in > J Am Chem Soc in a paper on homoaromaticity about 10-15 years ago. > > E. Lewars > ==== > > -------- Original Message -------- > Subject: CCL:1,3,5-cyclohexatriene > Date: Thu, 11 May 2000 09:21:17 +0400 > From: Valentine Ananikov > Organization: IOC > To: CCL_post > > Dear List Members, > > Does anybody have an information about predicted structure and > stability for 1,3,5-cyclohexatriene? > > I mean a six-membered ring with alternating single and double > C-C bonds, but without aromatic pi-electrons delocalization due > to non-planar conformation (i.e. non-planar benzene isomer). > Would such structure exist in principle? > > Thanks! Valentin. > > ==================================================================== > , , , , > Valentine P. Ananikov |\\\\ ////| /////| > NMR Group | \\\|/// | ///// | > ND Zelinsky Institute of Organic Chemistry | |~~~| | |~~~| | > Leninsky Prospect 47 | |===| | |===| | > Moscow 117913 | | | | | | | > Russia | | A | | | Z | | > \ | | / | | / > e-mail: val@cacr.ioc.ac.ru \|===|/ |===|/ > http://nmr.ioc.ac.ru/Staff/AnanikovVP/ '---' '---' > Fax +7 (095)1355328 Phone +7 (095)9383536 > ==================================================================== ==================================================================== , , , , Valentine P. Ananikov |\\\\ ////| /////| NMR Group | \\\|/// | ///// | ND Zelinsky Institute of Organic Chemistry | |~~~| | |~~~| | Leninsky Prospect 47 | |===| | |===| | Moscow 117913 | | | | | | | Russia | | A | | | Z | | \ | | / | | / e-mail: val@cacr.ioc.ac.ru \|===|/ |===|/ http://nmr.ioc.ac.ru/Staff/AnanikovVP/ '---' '---' Fax +7 (095)1355328 Phone +7 (095)9383536 ==================================================================== From chemistry-request@server.ccl.net Mon May 22 03:01:43 2000 Received: from gwdu42.gwdg.de (root@gwdu42.gwdg.de [134.76.10.26]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id DAA08605 for ; Mon, 22 May 2000 03:01:42 -0400 Received: from mbp-sgi3.inet.dkfz-heidelberg.de ([193.174.59.123] helo=mbp-sgi3) by gwdu42.gwdg.de with smtp (Exim 3.12 #1) id 12tmDW-0000Un-00 for chemistry@ccl.net; Mon, 22 May 2000 09:01:34 +0200 Sender: platzer@ccl.net Message-ID: <392959A3.41C6@gwdg.de> Date: Mon, 22 May 2000 09:00:35 -0700 From: Ute Platzer X-Mailer: Mozilla 3.0 (X11; I; IRIX 5.3 IP22) MIME-Version: 1.0 To: chemistry@ccl.net Subject: large Discover history files due to water molecules Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hello, I've got a problem with analyzing data gathered during a MD simulation with Discover and InsightII (a protein solvated in Water, about 16000 atoms). The .his file, where the trajectory data is stored, is huge (more then 1 Gb) because the coordinates of water molecules are stored also. When I try to load the trajectory into InsightII, the program chrashes because of insufficient memory. As I'm only interested in the coordinates of the protein itself I wondered wether there is a possibility to tell Discover not to save the water molecule coordinates in the trajectory file. I'd be happy if someone could help me. Ute ------------------------------------ Ute Platzer Molecular Biophysics Department DKFZ (German Cancer Research Center) Heidelberg, Germany mailto:uplatze@gwdg.de From chemistry-request@server.ccl.net Mon May 22 06:54:46 2000 Received: from szermierz.uni.wroc.pl (szermierz.uni.wroc.pl [156.17.93.253]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id GAA10532 for ; Mon, 22 May 2000 06:54:40 -0400 Received: from wchuwr.chem.uni.wroc.pl (wchuwr.chem.uni.wroc.pl [156.17.103.193]) by szermierz.uni.wroc.pl (8.9.1/8.9.1) with ESMTP id NAA11792 for ; Mon, 22 May 2000 13:48:51 +0200 (CEST) Received: from WCHUWR/SpoolDir by wchuwr.chem.uni.wroc.pl (Mercury 1.44); 22 May 00 12:56:33 MET Received: from SpoolDir by WCHUWR (Mercury 1.44); 22 May 00 12:56:13 MET From: "Adrian Radomir Jaszewski" Organization: University of Wroclaw (Chemistry) To: chemistry@server.ccl.net Date: Mon, 22 May 2000 12:56:08 MET Subject: SUMMARY: ab initio hyperfine constants Priority: normal X-mailer: Pegasus Mail/Windows (v1.22) Message-ID: <7EFCA4D89@wchuwr.chem.uni.wroc.pl> 22 May 2000 SUMMARY of the answers to AB INITIO HYPERFINE CONSTANTS question Dear CCL'ers, I asked a question about the hyperfine constants from ab initio methods (listed at the end of this message) two weeks ago. Thanks a lot to Dr. David Feller. You are the only person who has replied. I appreciate your efforts highly. Many people asked me to summarize the replies in return. Hence I present this summary compiled from two letters from AUTHOR of the paper cited in my question. Good luck with your calculations. Adrian ------------------------EXCERPTS:-------------------------- I think there may be a misunderstanding here. In our JCP paper on NO we used a finite field approach to computing the isotropic hyperfine properties with methods like UMP2, UMP3, UMP4 and UQCISD(T). The spin denisty matrix wasn't involved. As far as I know, it isn't possible to obtain a UQCISD(T) density matrix from Gaussian. But maybe that has changed. The Gaussian options that we used are as follows: # UQCISD(T)=FULL/GEN SCF=(DIRECT,NOSINGLEPOINT) # UNITS=AU FIELD=F(2)-4 I don't have access to that paper from home (where I'm writing this), but I believe we did 2 point differencing to predict the isotropic hyperfine property at each nucleus. In our procedure, the isotropic hyperfine property is given as the derivative of the energy with respect to the applied field, evaluated at zero field. For example, we ran calculations at +/- 0.0001 or +/-0.0004 andused a 2-point formula to obtain the derivative at zero field. (f+) - (f-)/2*delta, where f+ is the energy with the positive field and f- is the energy at negative field. Delta is the field strength. That just gives you the raw value of the property in atomic units. You then need to convert that raw value into something useful, like MHz or G. This has to be done for each nucleus of interest. You should be sure to correlate *ALL* electrons, as the property is very sensistive to core correlation. The other methods require nothing more than changing the method indicated in the options. David Feller | d3e102@emsl.pnl.gov Environmental Molecular Sciences Lab., K8-91| Box 999 Pacific Northwest National Laboratory | Richland, WA 99352 | Fax: 509-375-6631 ----------------------MY QUESTION--------------------------- I have read some papers of Chipman, Feller and Carmichael about evaluation of the isotropic hyperfine coupling constants (HFCC's) from ab initio methods. Unfortunately, I have got some problems in the application (Gaussian94/98) of the procedures described there, that are mainly of technical nature. Let me use the computations of the isotropic splittings for NO radical (2 PI) as an example [D.Feller et al. J.Chem.Phys. 99 (1993) 2829]. Determination of the isotropic hyperfine constants using a given method (QCISD for instance), that are listed as a part of the population analysis output, requires inclusion of the keyword Density=Current in the job's route section i.e.: %chk=filename # UQCISD=(Conver=8,Full)/Gen SCF=(Tight,NoDIIS,MaxCyc=256) # Density=Current Prop=EPR Title section 0 2 o 0.000000 0.000000 0.000000 n 1.150431 0.000000 0.000000 basis set description Of course, SCF and Prop=EPR keywords denote single point (but with tight convergence criteria) calculations and evaluation of the anisotropic hyperfine couplings, respectively. The main problem is that the generalized densities are available only for HF, MP2, MP3, MP4(SDQ), QCISD, CCD and CISD methods. My question are: 1. How to calculate HFCC's using CCSD method that are included in Table II of the originally paper? 2. How to calculate HFCC's using QCISD(T) method? One can do this from spin densities derived by finite-field perturbation theory in the presence of small Fermi contact field at each nucleus in turn but what changes in the input file should be made (in comparison with this listed above). Should I use the Field=F(AtomNumber)FileSize command? 3. How to calculate HFCC's using CCSD(T) method? 4. How to calculate HFCC's using QCISD(TQ) method? Perturbation theory approach allows the inclusion of the effect of quadruple replacement through fifth order but how to avoid Density keyword restrictions and what commands should be added to the route section of the input file? From chemistry-request@server.ccl.net Mon May 22 08:08:21 2000 Received: from myamlak.ch.uj.edu.pl (myamlak.ch.uj.edu.pl [149.156.71.18]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id IAA10922 for ; Mon, 22 May 2000 08:08:12 -0400 Received: from localhost (borowski@localhost) by myamlak.ch.uj.edu.pl (8.9.3/8.9.3) with ESMTP id OAA02437 for ; Mon, 22 May 2000 14:00:42 +0200 (MET DST) Date: Mon, 22 May 2000 14:00:42 +0200 (MET DST) From: Tomasz Borowski X-Sender: borowski@myamlak.ch.uj.edu.pl To: chemistry@ccl.net Subject: TDDFT_in_G98 Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear CCL Users, I've got a question about TD DFT method (in Gaussian 98). Is it possible to calculate excitations energies to the excited states different from the ground state by 1 excitation within alpha framework and 1 excitation within beta? (using unrestricted formalism). Tomek Borowski. From chemistry-request@server.ccl.net Mon May 22 05:41:07 2000 Received: from email.guomai.sh.cn (mpudzuasmn@e4000.guomai.sh.cn [202.96.206.72]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id FAA09444 for ; Mon, 22 May 2000 05:41:06 -0400 Received: from guomai.sh.cn ([202.101.13.187]) by email.guomai.sh.cn (Sun Internet Mail Server sims.3.5.1999.07.30.00.05.p8) with ESMTP id <0FUY00D3XGLP4P@email.guomai.sh.cn> for CHEMISTRY@ccl.net; Mon, 22 May 2000 17:49:11 +0800 (CST) Date: Mon, 22 May 2000 17:39:07 +0800 From: Yubo Fan Subject: CheckPoint file converting To: CHEMISTRY@ccl.net Message-id: <3929003A.2E8253C@guomai.sh.cn> MIME-version: 1.0 X-Mailer: Mozilla 4.7 [en] (Win98; I) Content-type: text/plain; charset=us-ascii Content-transfer-encoding: 7bit X-Accept-Language: en Hi, everyone, Are there some ways to convert G98 formatted checkpoint files into G94 ones? The OSs I am using are AIX 6.2, Redhat Linux 6.1 and Windows 98. Thanks in advance. -- ============================================================= 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 ============================================================= From chemistry-request@server.ccl.net Mon May 22 11:59:01 2000 Received: from postal.ucc.uno.edu (postal.ucc.uno.edu [137.30.1.80]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id LAA11916 for ; Mon, 22 May 2000 11:59:00 -0400 Received: from CONVERSION-DAEMON by postal.ucc.uno.edu (PMDF V5.2-32 #39187) id <0FUY00A01XPU5W@postal.ucc.uno.edu> for chemistry@ccl.net; Mon, 22 May 2000 10:58:42 -0500 (CDT) Received: from uno.edu (cuzco.chem.uno.edu [137.30.57.85]) by postal.ucc.uno.edu (PMDF V5.2-32 #39187) with ESMTP id <0FUY00O42XPT2A@postal.ucc.uno.edu> for chemistry@ccl.net; Mon, 22 May 2000 10:58:42 -0500 (CDT) Date: Mon, 22 May 2000 10:55:05 -0500 From: Monica Concha Subject: Summary To: "chemistry@ccl.net" Message-id: <39295852.BFBF5873@uno.edu> Organization: University of New Orleans MIME-version: 1.0 X-Mailer: Mozilla 4.72 (Macintosh; U; PPC) Content-type: MULTIPART/MIXED; BOUNDARY="Boundary_(ID_FGFcxRm0VzPZIcTbfRPmeQ)" X-Accept-Language: en,pdf This is a multi-part message in MIME format. --Boundary_(ID_FGFcxRm0VzPZIcTbfRPmeQ) Content-type: MULTIPART/ALTERNATIVE; BOUNDARY="Boundary_(ID_sPDG/K5qOlTPwTN4rnRV+Q)" --Boundary_(ID_sPDG/K5qOlTPwTN4rnRV+Q) Content-type: text/plain; charset=iso-8859-1; x-mac-type=54455854; x-mac-creator=4D4F5353 Content-transfer-encoding: 8BIT Dear CCl'ers, A few wanted me to summarize the replies to the CCL list. Here it comes, and thanks to the six people who took time to respond. Monica C. Concha Research Associate Dept. Of Chemistry University of New Orleans New Orleans LA 70148 E-mail mconcha@uno.edu ********************************************************************* Q: I have been trying to optimize the vanadium dimer with multiplicity of 3, using various dft methods. The problem is that depending on the initial bond length, the dimer optimizes to different bond lengths with different energies, and differ s**2 values. The bond lengths only differ by about 0.01 Angstroms but the energies differ by 35 kcal. The odd thing is that the lowest energy corresponds to an s**2 value of 2.55 rather than the expected value of 2.0. Any suggestions? ********************************************************************** A: Hi Monica, If you haven't done much work with metal clusters before, you're quickly going to find out they are much tougher than simple organics. The problem is there are lots of low-lying excited states arising from low overlap of the incomplete d shells. In the case of V2, you have two dominantly s1d4 atoms bonded to one another, with the other atomic states, d5 and s2d3, probably mixing in. This gives you a large number of possible spin and orbital combinations to work with. As for your DFT calculations, it's a given that you have to specify spin. But in these cases, you may also have to play with the orbital occupations in the initial guess. It's very easy for most codes to converge to excited states of these molecules. The only solid solution is to be very thorough. You've found two different triplet states already, but it might not be guaranteed that either is actually the lowest energy triplet (or the ground state for that matter!). Be aware of what states (d orbital occupations) are being converged. Try switching around the orbital occupations and converging some other states. Most codes offer some way of doing this either with the default initial guess or with a restart file. If you're worried about spin contamination, you might want to try a restricted open-shell approach. I'd suggest sticking with unrestricted, though. In this case, I'd probably turn off any symmetry restrictions to allow the spins to localize. I haven't reviewed the literature on V2, but I'd guess the ground state is singlet with one V alpha-spin s1d4 and the other beta-spin s1d4. The strong exchange interaction between the d orbitals should be enough to localize the spin. But low-lying spin states could extend up to nonet states. Good Luck, Jason Perry **************************************************************** Hi Mónica: You should look at works of Casalot (Marsielle) on V-V bond in V2O4. Felicidades!!! Julio César Llópiz Yurell IMRE, UH Zapata y G, Habana 10400, CUBA Tel (537) 781182 Fax (537) 334247 ****************************************************************** Hi Monika, >from your non-integer value for I conclude that you used an unrestricted DFT method. Since V2 has 10 valence electrons but 9 bonding and 9 antibonding combinations of atomic valence orbitals, I assume that you converged to two different electronic states. Although the p-functions of transition metals are not occupied in the free atoms, they DO participate in bond formation (e.g. 18 valence electron rule for TM complexes). You can check that by printing out the MO vectors (i.e. info on what basis functions/atomic orbitals participate in a given MO) and compare them for your two optimized structures. If you have two different states, you need a multireference method like CASSCF or MR-CI (maybe a powerful single reference correlation method like CCSDT works too, but that can only be decided after seeing the output from that calculation). Anyhow, putting enough ligands around your vanadiums to give them 18 valence electrons, each, makes the molecule well-behaved again. Stefan ______________________________________________________________________ Dr. Stefan Fau | fau@qtp.ufl.edu Quantum Theory Project | (352) 392-6714 University of Florida Gainesville, FL 32611-8435 ******************************************************************* Hi, Before optimizing the V-V bond length, you need to sort out the electronic structure. That is, look at the initial guess for starters, try and get a converged single point SCF and look at the S**2 and occupation. Is it reasonable? Then you can optimize the V-V bond length for whatever state you have found. If you have spin contamination problems, you might try an rohf calulation first to insure a reasonable spin function. It sounds like you have one triplet V-V state that is fully optimized without spin contamination problems. Compare the electronic occupation with the 'bad' state. Perhaps you can switch around some orbitals in your higher energy but well behaved case to find a lower energy triplet. Perhaps a triplet is a very high energy/unreasonable multiplicity for V2? Atomic spectral tables show the lowest doublet V neutral atom to be 10,900 cm-1 above ground state V. The lowest V doublet without an s2 population is 18,800 above the ground state. So you're paying a 4.7eV promotion simply to form reasonable doublets to form the V2 triplet. I don't have much experience with metal cluster calculations though. Hope this helps! - John *********************************************************** Dear Monica, I've recently come across a similar problem with VO (4 sigma ground state). The problem was, that initial guess of occupied MO was totally wrong (the distribution of electrons between different irreps). As I'm using G98, the solution was quite easy: Guess=Alter (+ appropriate labes of MO to exchange), and that was enough to get the proper electronic state. Tomek Borowski Chemistry Department Jagiellonian Univ. Krakow ********************************************************* Dear Monica, did you check the stability of your wavefunction? You mix in higher spin states as can be seen from the S2 value of 2.55 If you need help, please email directly to thomas.strassner@ch.tum.de Yours sincerely Thomas Strassner ********************************************************* --Boundary_(ID_sPDG/K5qOlTPwTN4rnRV+Q) Content-type: text/html; charset=us-ascii Content-transfer-encoding: 7BIT Dear CCl'ers,

A few wanted me to summarize the replies to the CCL list.  Here it comes,
and thanks to the six people who took time to respond.

Monica C. Concha
Research Associate
Dept. Of Chemistry
University of New Orleans
New Orleans LA 70148
E-mail mconcha@uno.edu
 

*********************************************************************
Q:

   I have been trying to optimize the vanadium dimer with multiplicity
of 3, using various dft methods. The problem is that depending on the
initial bond length, the dimer optimizes to different bond lengths with
different energies, and differ s**2 values.  The bond lengths only
differ
by about 0.01 Angstroms but the energies differ by 35 kcal.  The odd
thing is that the lowest energy corresponds to an s**2 value of 2.55
rather than the expected value of 2.0. Any suggestions?
**********************************************************************
A:

Hi Monica,

    If you haven't done much work with metal clusters before, you're quickly going
to find out they are much tougher than simple organics.  The problem is there are
lots of low-lying excited states arising from low overlap of the incomplete d
shells.  In the case of V2, you have two dominantly s1d4 atoms bonded to one
another, with the other atomic states, d5 and s2d3, probably mixing in.  This gives
you a large number of possible spin and orbital combinations to work with.
    As for your DFT calculations, it's a given that you have to specify spin.  But
in these cases, you may also have to play with the orbital occupations in the
initial guess.  It's very easy for most codes to converge to excited states of
these molecules.  The only solid solution is to be very thorough.  You've found two
different triplet states already, but it might not be guaranteed that either is
actually the lowest energy triplet (or the ground state for that matter!).  Be
aware of what states (d orbital occupations) are being converged.  Try switching
around the orbital occupations and converging some other states.  Most codes offer
some way of doing this either with the default initial guess or with a restart
file.
    If you're worried about spin contamination, you might want to try a restricted
open-shell approach.  I'd suggest sticking with unrestricted, though.  In this
case, I'd probably turn off any symmetry restrictions to allow the spins to
localize.  I haven't reviewed the literature on V2, but I'd guess the ground state
is singlet with one V alpha-spin s1d4 and the other beta-spin s1d4.  The strong
exchange interaction between the d orbitals should be enough to localize the spin.
But low-lying spin states could extend up to nonet states.
    Good Luck,

    Jason Perry

****************************************************************

Hi Mónica:

You should look at works of Casalot (Marsielle) on V-V bond in V2O4.

<Andre.Casalot@newsup.univ-mrs.fr>
 

Felicidades!!!

Julio César Llópiz Yurell
IMRE, UH
Zapata y G, Habana 10400, CUBA
Tel (537) 781182  Fax (537) 334247

******************************************************************
Hi Monika,

from your non-integer value for <S^2> I conclude that
you used an unrestricted DFT method. Since V2 has
10 valence electrons but 9 bonding and 9 antibonding
combinations of atomic valence orbitals, I assume that
you converged to two different electronic states.

Although the p-functions of transition metals are not
occupied in the free atoms, they DO participate in bond
formation (e.g. 18 valence electron rule for TM complexes).
You can check that by printing out the MO vectors (i.e.
info on what basis functions/atomic orbitals participate in
a given MO) and compare them for your two optimized
structures.

If you have two different states, you need a multireference
method like CASSCF or MR-CI (maybe a powerful single
reference correlation method like CCSDT works too, but
that can only be decided after seeing the output from that
calculation). Anyhow, putting enough ligands around your
vanadiums to give them 18 valence electrons,
each, makes the molecule well-behaved again.

Stefan
______________________________________________________________________
Dr. Stefan Fau                    |      fau@qtp.ufl.edu
Quantum Theory Project     |     (352) 392-6714
University of Florida
Gainesville, FL 32611-8435
*******************************************************************
Hi,

  Before optimizing the V-V bond length, you need to sort out
the electronic structure.  That is, look at the initial guess
for starters, try and get a converged single point SCF and look
at the S**2 and occupation.  Is it reasonable?  Then you can
optimize the V-V bond length for whatever state you have found.
If you have spin contamination problems, you might try an rohf
calulation first to insure a reasonable spin function.
  It sounds like you have one triplet V-V state that is fully
optimized without spin contamination problems.  Compare the
electronic occupation with the 'bad' state.  Perhaps you can
switch around some orbitals in your higher energy but well
behaved case to find a lower energy triplet.  Perhaps a triplet
is a very high energy/unreasonable multiplicity for V2?  Atomic
spectral tables show the lowest doublet V neutral atom to be
10,900 cm-1 above ground state V.  The lowest V doublet without
an s2 population is 18,800 above the ground state.  So you're
paying a 4.7eV promotion simply to form reasonable doublets to
form the V2 triplet.  I don't have much experience with metal
cluster calculations though.  Hope this helps!

    - John
***********************************************************
Dear Monica,

I've recently come across a similar problem with VO (4 sigma ground
state). The problem was, that initial guess of occupied MO was totally
wrong (the distribution of electrons between different irreps). As I'm
using G98, the solution was quite easy: Guess=Alter (+ appropriate
labes of MO to exchange), and that was enough to get the proper electronic
state.
 

Tomek Borowski
Chemistry Department
Jagiellonian Univ.
Krakow

*********************************************************
Dear Monica,

did you check the stability of your wavefunction? You mix in higher spin
states as
can be seen from the S2 value of 2.55

If you need help, please email directly to

thomas.strassner@ch.tum.de
 

Yours sincerely

Thomas Strassner

*********************************************************
  --Boundary_(ID_sPDG/K5qOlTPwTN4rnRV+Q)-- --Boundary_(ID_FGFcxRm0VzPZIcTbfRPmeQ) Content-type: text/x-vcard; charset=us-ascii; name=mconcha.vcf Content-description: Card for Monica Concha Content-disposition: attachment; filename=mconcha.vcf Content-transfer-encoding: 7BIT begin:vcard n:Concha;Monica C. tel;cell:504-460-6424 tel;fax:504-280-6860 tel;home:504- 456-2325 tel;work:504-280-7216 x-mozilla-html:FALSE org:University of New Orleans;Chemistry adr:;;Lakeshore;New Orleans;LA;70148;USA version:2.1 email;internet:mconcha@uno.edu title:Research Associate x-mozilla-cpt:;1 fn:Monica C. Concha end:vcard --Boundary_(ID_FGFcxRm0VzPZIcTbfRPmeQ)-- From chemistry-request@server.ccl.net Mon May 22 21:01:13 2000 Received: from uvaix7e1.comp.UVic.CA (root@uvaix7e1.comp.UVic.CA [142.104.5.107]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id VAA16392 for ; Mon, 22 May 2000 21:01:13 -0400 Received: from p17-98.dialup.UVic.CA (p17-98.dialup.UVic.CA [142.104.17.98]) by uvaix7e1.comp.UVic.CA (8.9.3/8.9.3) with SMTP id SAA49472 for ; Mon, 22 May 2000 18:01:07 -0700 From: Roy Jensen To: chemistry@ccl.net Subject: metal halogen/sulfur clusters Date: Mon, 22 May 2000 18:01:09 -0700 Message-ID: X-Mailer: Forte Agent 1.8/32.548 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by server.ccl.net id VAA16393 I am looking for a method that reasonable predicts the structure of transition metal--halogen or metal--sulfur clusters, Metal(x)Halo/Sulfur(y) where 1<=x<=6 and 1<=y<=10. We have Gaussian and Hyperchem available; both running on PC's. Our goal is to compliment our expt data with reasonable predictions on structure and stability and explain some of the trends we observe. I will summarize responses. Roy Jensen