From owner-chemistry@ccl.net Tue Dec 13 13:15:00 2011 From: "Thomas Exner thomas.exner . uni-konstanz.de" To: CCL Subject: CCL:G: CASSCF problems Message-Id: <-46027-111213131428-23306-t9c+wMkFtzPS/dQisBe5vw,+,server.ccl.net> X-Original-From: Thomas Exner Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Date: Tue, 13 Dec 2011 19:14:20 +0100 MIME-Version: 1.0 Sent to CCL by: Thomas Exner [thomas.exner*|*uni-konstanz.de] Dear Jürgen: Thank you very much for pointing me to the FON-DFT approach. I will definitely look into it. But I still think that standard CASSCF should be able to get it right. Perhaps I make a complete fool out of me, anyway: In an MO picture, there are the two degenerated states (pi_x and pi_y) and HF and DFT, which take no non-dynamic correlation into account, should convert to one of these. But the NO molecule should show a symmetric electron distribution, which shows, in my opinion, that the MO scheme is misleading. Fractional occupation numbers help here, since one can put half an electron in each of the two degenerated pi orbitals. But is that not exactly what CASSCF is meant for. By combining multiple electron configurations, the calculation should be able (in a very simplified way to demonstrate my point) to take the two configuration with the unpaired electron in the pi_x orbital and in the pi_y orbital, respectively, with equal contribution. This would then result in an electron occupation of 0.5 in both orbitals, exactly what I expect. Any comments on that or a reason, why I am wrong? And, really no suggestions for my second question? "Additionally, I have a larger system for which I also perform casscf calculations. Ground state simulations and also the first excited state using the ground state geometry are fine. Energy optimization in the excited state also starts ok but after some steps the calculation does not converge anymore. Use of "use=l506" as proposed in the g09 manual did not help. Also no luck with increasing the maxcycle or starting with an other conformation. Is there anything else I can try? Perhaps there are some options for the optimizer that he does not jump into the bad region with the convergence problems. Unfortunately, the "sleazy" and the "qc" keyword for scf cannot be used with casscf optimization." Thanks. Thomas Jürgen Gräfenstein jurgen**chem.gu.se wrote: > > Sent to CCL by: =?iso-8859-1?Q?J=FCrgen_Gr=E4fenstein?= [jurgen:_:chem.gu.se] > Dear Thomas, > > Everything appears to be all right. The state you seek is twofold degenerate (Pi_x, Pi_y), and a quantum chemical calculation gets you one of the states. In order to get an equal distribution between Pi_x and Pi_y youwould need a fractional-occupation-number (FON) CASSCF. I am not sure whether something like this has been worked out and implemented somewhere for CASSCF. (FON-DFT is implemented in Gaussian). > > Best regards, > Jürgen > > > ---- > Jürgen Gräfenstein > University of Gothenburg > Dept of Chemistry > Jurgen.Grafenstein!A!chem.gu.se > > > On 10 Dec, 2011, at 15:09 , Thomas Exner thomas.exner%a%uni-konstanz.dewrote: > >> >> Sent to CCL by: Thomas Exner [thomas.exner%%uni-konstanz.de] >> Dear CCLers: >> >> I am running in some problem with CASSCF calculations using g09, for which I have no explanation, and I hope that somebody out there can help me. I would like to start with a relative simple system: NO. For this system I would expect that the unpaired electron is distributed equally between the two antibonding pi orbitals. But I get an occupation number of exactly 1 for the first and 0 for the second orbital using a casscf(1,2) calculation. In a casscf(5,4) including the two bonding pi orbitals, there is again almost exactly 1 electron in the one orbital and a few percent ofan electron in the other. The additional electron occupation is taken from the bonding orbitals. Has somebody an idea, what I am going wrong, or is my assumption of equal distribution wrong? >> >> Here is the input (pretty simplex, eh): >> # casscf(5,4)/sto-3g nosymm >> >> NO 1 >> >> 0 2 >> O >> N 1 B1 >> >> B1 1.25247685> > -- ________________________________________________________________________________ Dr. Thomas E. Exner Fachbereich Chemie Universität Konstanz 78457 Konstanz Tel.: +49-(0)7531-882015 Fax: +49-(0)7531-883587 Email: thomas.exner .. uni-konstanz.de ________________________________________________________________________________ From owner-chemistry@ccl.net Tue Dec 13 16:07:00 2011 From: "Brian Salter-Duke brian.james.duke * gmail.com" To: CCL Subject: CCL:G: CASSCF problems Message-Id: <-46028-111213160322-921-eJ9s/Mp8/sWLLLm7VN7KNw_._server.ccl.net> X-Original-From: Brian Salter-Duke Content-Disposition: inline Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=iso-8859-1 Date: Wed, 14 Dec 2011 08:01:22 +1100 MIME-Version: 1.0 Sent to CCL by: Brian Salter-Duke [brian.james.duke]^[gmail.com] On Tue, Dec 13, 2011 at 07:14:20PM +0100, Thomas Exner thomas.exner . uni-konstanz.de wrote: > > Sent to CCL by: Thomas Exner [thomas.exner*|*uni-konstanz.de] > Dear Jürgen: > > Thank you very much for pointing me to the FON-DFT approach. I will > definitely look into it. But I still think that standard CASSCF should > be able to get it right. Perhaps I make a complete fool out of me, > anyway: In an MO picture, there are the two degenerated states (pi_x and > pi_y) and HF and DFT, which take no non-dynamic correlation into > account, should convert to one of these. But the NO molecule should show > a symmetric electron distribution, which shows, in my opinion, that the > MO scheme is misleading. Fractional occupation numbers help here, since > one can put half an electron in each of the two degenerated pi orbitals. > But is that not exactly what CASSCF is meant for. By combining multiple > electron configurations, the calculation should be able (in a very > simplified way to demonstrate my point) to take the two configuration > with the unpaired electron in the pi_x orbital and in the pi_y orbital, > respectively, with equal contribution. This would then result in an > electron occupation of 0.5 in both orbitals, exactly what I expect. Any > comments on that or a reason, why I am wrong? I think the answer is that either HF solution gives the same energy as txpeh mix. However, it used to be possable back in the 1970 in the ATMOL program in UK to run what was called the symmetry equivalenced Hartree-Fock method (SEHRF) which gives equal weight to the odd electron being in pi-x and pi-y. See M F Guest and V R Saunders, Mol Phys., 28, 819, (1974). I do not know whether it is in any other code. It might be in GAMESS(UK) which is still developed by Martin Guest. Brian. > And, really no suggestions for my second question? > "Additionally, I have a larger system for which I also perform casscf > calculations. Ground state simulations and also the first excited state > using the ground state geometry are fine. Energy optimization in the > excited state also starts ok but after some steps the calculation does > not converge anymore. Use of "use=l506" as proposed in the g09 manual > did not help. Also no luck with increasing the maxcycle or starting with > an other conformation. Is there anything else I can try? Perhaps there > are some options for the optimizer that he does not jump into the bad > region with the convergence problems. Unfortunately, the "sleazy" and > the "qc" keyword for scf cannot be used with casscf optimization." > > Thanks. > Thomas > > > Jürgen Gräfenstein jurgen**chem.gu.se wrote: >> >> Sent to CCL by: =?iso-8859-1?Q?J=FCrgen_Gr=E4fenstein?= [jurgen:_:chem.gu.se] >> Dear Thomas, >> >> Everything appears to be all right. The state you seek is twofold degenerate (Pi_x, Pi_y), and a quantum chemical calculation gets you one of the states. In order to get an equal distribution between Pi_x and Pi_y youwould need a fractional-occupation-number (FON) CASSCF. I am not sure whether something like this has been worked out and implemented somewhere for CASSCF. (FON-DFT is implemented in Gaussian). >> >> Best regards, >> Jürgen >> >> >> ---- >> Jürgen Gräfenstein >> University of Gothenburg >> Dept of Chemistry >> Jurgen.Grafenstein!A!chem.gu.se >> >> >> On 10 Dec, 2011, at 15:09 , Thomas Exner thomas.exner%a%uni-konstanz.dewrote: >> >>> >>> Sent to CCL by: Thomas Exner [thomas.exner%%uni-konstanz.de] >>> Dear CCLers: >>> >>> I am running in some problem with CASSCF calculations using g09, for which I have no explanation, and I hope that somebody out there can help me. I would like to start with a relative simple system: NO. For this system I would expect that the unpaired electron is distributed equally between the two antibonding pi orbitals. But I get an occupation number of exactly 1 for the first and 0 for the second orbital using a casscf(1,2) calculation. In a casscf(5,4) including the two bonding pi orbitals, there is again almost exactly 1 electron in the one orbital and a few percent ofan electron in the other. The additional electron occupation is taken from the bonding orbitals. Has somebody an idea, what I am going wrong, or is my assumption of equal distribution wrong? >>> >>> Here is the input (pretty simplex, eh): >>> # casscf(5,4)/sto-3g nosymm >>> >>> NO 1 >>> >>> 0 2 >>> O >>> N 1 B1 >>> >>> B1 1.25247685> >> > > -- > ________________________________________________________________________________ > > Dr. Thomas E. Exner > Fachbereich Chemie > Universität Konstanz > 78457 Konstanz > > Tel.: +49-(0)7531-882015 > Fax: +49-(0)7531-883587 > Email: thomas.exner##uni-konstanz.de > ________________________________________________________________________________http://www.ccl.net/chemistry/sub_unsub.shtmlConferences: > http://server.ccl.net/chemistry/announcements/conferences/> -- Brian Salter-Duke (Brian Duke) Brian.Salter-Duke**monash.edu Adjunct Associate Professor Monash Institute of Pharmaceutical Sciences Monash University Parkville Campus, VIC 3052, Australia From owner-chemistry@ccl.net Tue Dec 13 16:44:00 2011 From: "Kirk Peterson kipeters ~ wsu.edu" To: CCL Subject: CCL:G: CASSCF problems Message-Id: <-46029-111213164242-1870-nM9HDi7z4eLaYBu6Rd7UMw!^!server.ccl.net> X-Original-From: Kirk Peterson Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=iso-8859-1 Date: Tue, 13 Dec 2011 13:42:33 -0800 Mime-Version: 1.0 (Apple Message framework v1251.1) Sent to CCL by: Kirk Peterson [kipeters+/-wsu.edu] Dear Thomas, the calculation that Brian suggests below is easily done with Molpro by carrying out a state-averaged CASSCF or HF calculation. In this case the Pi_x and Pi_y states are computed with equal weights and the final natural orbital occupation numbers will show an occupancy of 0.5 for each of the open-shell pi orbitals. I always use this type of symmetry equivalencing for degenerate states of linear molecules (Pi, Delta, etc.) and particularly for open-shell atoms. regards, Kirk On Dec 13, 2011, at 1:01 PM, Brian Salter-Duke brian.james.duke * gmail.com wrote: > > Sent to CCL by: Brian Salter-Duke [brian.james.duke]^[gmail.com] > On Tue, Dec 13, 2011 at 07:14:20PM +0100, Thomas Exner thomas.exner . uni-konstanz.de wrote: >> >> Sent to CCL by: Thomas Exner [thomas.exner*|*uni-konstanz.de] >> Dear Jürgen: >> >> Thank you very much for pointing me to the FON-DFT approach. I will >> definitely look into it. But I still think that standard CASSCF should >> be able to get it right. Perhaps I make a complete fool out of me, >> anyway: In an MO picture, there are the two degenerated states (pi_x and >> pi_y) and HF and DFT, which take no non-dynamic correlation into >> account, should convert to one of these. But the NO molecule should show >> a symmetric electron distribution, which shows, in my opinion, that the >> MO scheme is misleading. Fractional occupation numbers help here, since >> one can put half an electron in each of the two degenerated pi orbitals. >> But is that not exactly what CASSCF is meant for. By combining multiple >> electron configurations, the calculation should be able (in a very >> simplified way to demonstrate my point) to take the two configuration >> with the unpaired electron in the pi_x orbital and in the pi_y orbital, >> respectively, with equal contribution. This would then result in an >> electron occupation of 0.5 in both orbitals, exactly what I expect. Any >> comments on that or a reason, why I am wrong? > > I think the answer is that either HF solution gives the same energy as > txpeh mix. However, it used to be possable back in the 1970 in the ATMOL > program in UK to run what was called the symmetry equivalenced > Hartree-Fock method (SEHRF) which gives equal weight to the odd electron > being in pi-x and pi-y. See M F Guest and V R Saunders, Mol Phys., 28, > 819, (1974). I do not know whether it is in any other code. It might be > in GAMESS(UK) which is still developed by Martin Guest. > > Brian. > >> And, really no suggestions for my second question? >> "Additionally, I have a larger system for which I also perform casscf >> calculations. Ground state simulations and also the first excited state >> using the ground state geometry are fine. Energy optimization in the >> excited state also starts ok but after some steps the calculation does >> not converge anymore. Use of "use=l506" as proposed in the g09 manual >> did not help. Also no luck with increasing the maxcycle or starting with >> an other conformation. Is there anything else I can try? Perhaps there >> are some options for the optimizer that he does not jump into the bad >> region with the convergence problems. Unfortunately, the "sleazy" and >> the "qc" keyword for scf cannot be used with casscf optimization." >> >> Thanks. >> Thomas >> >> >> Jürgen Gräfenstein jurgen**chem.gu.se wrote: >>> >>> Sent to CCL by: =?iso-8859-1?Q?J=FCrgen_Gr=E4fenstein?= [jurgen:_:chem.gu.se] >>> Dear Thomas, >>> >>> Everything appears to be all right. The state you seek is twofold degenerate (Pi_x, Pi_y), and a quantum chemical calculation gets you one of the states. In order to get an equal distribution between Pi_x and Pi_y youwould need a fractional-occupation-number (FON) CASSCF. I am not sure whether something like this has been worked out and implemented somewhere for CASSCF. (FON-DFT is implemented in Gaussian). >>> >>> Best regards, >>> Jürgen >>> >>> >>> ---- >>> Jürgen Gräfenstein >>> University of Gothenburg >>> Dept of Chemistry >>> Jurgen.Grafenstein!A!chem.gu.se >>> >>> >>> On 10 Dec, 2011, at 15:09 , Thomas Exner thomas.exner%a%uni-konstanz.dewrote: >>> >>>> >>>> Sent to CCL by: Thomas Exner [thomas.exner%%uni-konstanz.de] >>>> Dear CCLers: >>>> >>>> I am running in some problem with CASSCF calculations using g09, for which I have no explanation, and I hope that somebody out there can help me. I would like to start with a relative simple system: NO. For this system I would expect that the unpaired electron is distributed equally between the two antibonding pi orbitals. But I get an occupation number of exactly 1 for the first and 0 for the second orbital using a casscf(1,2) calculation. In a casscf(5,4) including the two bonding pi orbitals, there is again almost exactly 1 electron in the one orbital and a few percent ofan electron in the other. The additional electron occupation is taken from the bonding orbitals. Has somebody an idea, what I am going wrong, or is my assumption of equal distribution wrong? >>>> >>>> Here is the input (pretty simplex, eh): >>>> # casscf(5,4)/sto-3g nosymm >>>> >>>> NO 1 >>>> >>>> 0 2 >>>> O >>>> N 1 B1 >>>> >>>> B1 1.25247685> >>> >> >> -- >> ________________________________________________________________________________ >> >> Dr. Thomas E. Exner >> Fachbereich Chemie >> Universität Konstanz >> 78457 Konstanz >> >> Tel.: +49-(0)7531-882015 >> Fax: +49-(0)7531-883587 >> Email: thomas.exner##uni-konstanz.de >> ________________________________________________________________________________http://www.ccl.net/chemistry/sub_unsub.shtmlConferences: >> http://server.ccl.net/chemistry/announcements/conferences/> > > -- > Brian Salter-Duke (Brian Duke) Brian.Salter-Duke(a)monash.edu > Adjunct Associate Professor > Monash Institute of Pharmaceutical Sciences > Monash University Parkville Campus, VIC 3052, Australia> >