On Sa= t, Aug 20, 2016 at 5:03 AM, Marcel Swart marcel.swart/./icrea.cat <owner-chemistry _ ccl.net> wrot= e:

De= ar Ankur,

I would suggest to have a look at PQS (Baker, = Pulay and co-workers) or QUILD (Swart and co-workers).
Both use B= aker=E2=80=99s elegant solution to constrained optimizations.
Baker, "Constrained optimization in delocalized internal c= oordinates=E2=80=9D
Journal of Computational Chemistry 18, 1079 (= 1997)
http://dx.doi.org/1= 0.1002/(SICI)1096-987X(199706)18:8%3C1079::AID-JCC12%3E3.0.CO;2-8=

PQS:
http://www.pqs-chem.com/capab= ilities.php

QUILD:
http://www.marcelswart.eu/quild
https://www.scm.com/documentation/Quild/in= dex/index

Marcel

On 19 Aug 2016, at 22:33, Ankur Kumar Gupta ankkg= upt*indiana.edu <owner-chemistry*= ccl.net> wrote:

Sent to CCL by: "Ankur K= umar Gupta" [ankkgupt||indiana.edu]
Hello,

I have been reading about constrained o= ptimization. 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 coord= inates constant. Theoretically, we should get 3N-6 non-zero eigenvalues fro= m the force constant matrix (for a molecule having N nuclei) but if we appl= y 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 a= nd vibrational motion due to which the number of non-zero eigenvalues might= change. But for the sake of simplicity, we can talk about equilibrium geom= etries only. I use Gaussian 09 and I observed that the number of non-zero e= igenvalues did not change after constrained optimization. !
I know ther= e 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) af= ter the optimization.

Thank you
Ankur

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_= ____________________________________
Prof. Dr. Marcel Swart, FRSC
ICREA Research Professor at
Institut de Qu=C3=ADmica Computacional= i Cat=C3=A0lisi (IQCC)
Univ. Girona (Spain)

COST Action CM1305 (= ECOSTBio) chair
Girona Seminar 2016 organizer

IQCC di= rector

RSC Advances associate editor

= Young Academy of Europe member

web
http://www.marcelswart.eu
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addressbook://www.marcelswart.eu/MSwart.vcf