*From*: Brian Skinn <bskinn===alum.mit.edu>*Subject*: CCL:G: Constrained optimization and frequency calculation*Date*: Thu, 25 Aug 2016 07:35:11 -0400

Dr. Jensen, Apologies for the pedantry, but is "one-dimensional quantity" the proper term? Wouldn't, say, "order-one tensor quantity" be more accurate? That is to say, the gradient and each of the normal modes are individually 3N-dimensional, order-one tensor quantities, are they not? Best regards, Brian On Wed, Aug 24, 2016 at 3:27 PM, Frank Jensen frj===chem.au.dk < owner-chemistry+/-ccl.net> wrote: > Gaussian by default assumes that the frequency analysis is done at a > stationary point, and projects out the T+R to get 3N-6 frequencies. > > If you are at a non-stationary point, use Freq=Projected to also project > out the gradient, and thus get 3N-7 frequencies. > > Note that this provides 3N-7 frequencies, regardless of the number of > geometry constraints imposed, since the non-zero gradient is still only a > one-dimensional quantity. > > > > Frank > > > > Frank Jensen > > Assoc. Prof., Vice-Chair > > Dept. of Chemistry > > Aarhus University > > http://old.chem.au.dk/~frj > > > > *From:* owner-chemistry+frj==chem.au.dk+/-ccl.net [mailto: > owner-chemistry+frj==chem.au.dk+/-ccl.net] *On Behalf Of *Ankur Gupta > ankkgupt**umail.iu.edu > *Sent:* 24. august 2016 20:00 > *To:* Frank Jensen > *Subject:* CCL:G: Constrained optimization and frequency calculation > > > > Hello, > > Thank you Prof. Dr. M. Swart for answering my question. I found Baker's > paper really helpful. It discusses constrained optimization thoroughly but > it does not focus much on normal mode analysis. I am more concerned about > the frequencies that we get from the Hessian after constrained > optimization. The algorithm for constrained optimization has been > implemented in most of the computational chemistry software. But I am not > able to understand the frequencies that it shows after the constrained > optimization. > > Thank you > > Ankur > > > > On Sat, Aug 20, 2016 at 5:03 AM, Marcel Swart marcel.swart/./icrea.cat < > owner-chemistry[-]ccl.net> wrote: > > Dear Ankur, > > > > I would suggest to have a look at PQS (Baker, Pulay and co-workers) or > QUILD (Swart and co-workers). > > Both use Baker’s elegant solution to constrained optimizations. > > > > Baker, "Constrained optimization in delocalized internal coordinates” > > Journal of Computational Chemistry 18, 1079 (1997) > > http://dx.doi.org/10.1002/(SICI)1096-987X(199706)18:8% > 3C1079::AID-JCC12%3E3.0.CO;2-8 > > > > PQS: > > http://www.pqs-chem.com/capabilities.php > > > > QUILD: > > http://www.marcelswart.eu/quild > > https://www.scm.com/documentation/Quild/index/index > > > > Marcel > > > > On 19 Aug 2016, at 22:33, Ankur Kumar Gupta ankkgupt*indiana.edu < > owner-chemistry*ccl.net> wrote: > > > > > Sent to CCL by: "Ankur Kumar Gupta" [ankkgupt||indiana.edu] > Hello, > > I have been reading about constrained optimization. I have read several > papers related to the topic including the classic Reaction path Hamiltonian > for polyatomic molecules by Miller et al. This and other research articles > describe what is known as 'projection operator' method to do optimization > keeping one or more internal coordinates constant. Theoretically, we should > get 3N-6 non-zero eigenvalues from the force constant matrix (for a > molecule having N nuclei) but if we apply m number of constraints in the > molecule, we should obtain 3N-6-m non-zero eigenvalues (frequencies). Also, > in cases where the constraint corresponds to a non-equilibrium geometry, > there will be coupling between rotational and vibrational motion due to > which the number of non-zero eigenvalues might change. But for the sake of > simplicity, we can talk about equilibrium geometries only. I use Gaussian > 09 and I observed that the number of non-zero eigenvalues did not change > after constrained optimization. ! > I know there are many computational chemistry softwares out there and I > would like to know if there is a software which can do constrained > optimization correctly and give me the right number and magnitude of > eigenvalues (frequencies) after the optimization. > > Thank you > Ankur > > > > -= This is automatically added to each message by the mailing script =-> the strange characters on the top line to the * sign. You can also> > E-mail to subscribers: CHEMISTRY*ccl.net or use:> > E-mail to administrators: CHEMISTRY-REQUEST*ccl.net or use> <br> > > > > _____________________________________ > Prof. Dr. Marcel Swart, FRSC > > ICREA Research Professor at > Institut de Química Computacional i Catàlisi (IQCC) > Univ. Girona (Spain) > > COST Action CM1305 (ECOSTBio) chair > Girona Seminar 2016 organizer > > IQCC director > > RSC Advances associate editor > > Young Academy of Europe member > > > > web > http://www.marcelswart.eu > vCard > addressbook://www.marcelswart.eu/MSwart.vcf > > > > > > > >