From owner-chemistry@ccl.net Tue Sep 28 08:32:00 2021 From: "Sumangla Arora arorasumangla%gmail.com" To: CCL Subject: CCL: How to find barrier less transition state Message-Id: <-54459-210928083017-8774-B/P9hoRGJXI3BtuU6K9XnQ*_*server.ccl.net> X-Original-From: "Sumangla Arora" Date: Tue, 28 Sep 2021 08:30:15 -0400 Sent to CCL by: "Sumangla Arora" [arorasumangla*_*gmail.com] Dear All, I am having difficulty getting a transition state between two intermediates. When I run a guess structure, I got one imaginary mode. However, when I put this structure for OPTTS in orca, this structure is immediately converting into the product. To me, this transition state is barrier less. How can I find this transition state? or If suppose there is no transition state then how can I prove that? From owner-chemistry@ccl.net Tue Sep 28 12:44:00 2021 From: "Marcel Swart (GMail) marcel.swart.:.gmail.com" To: CCL Subject: CCL: How to find barrier less transition state Message-Id: <-54460-210928124223-30530-axU/BixYG2qMfhcpIpLayQ : server.ccl.net> X-Original-From: "Marcel Swart (GMail)" Content-Type: multipart/alternative; boundary="Apple-Mail=_60EC4447-C83B-4BDC-891F-F58E70EDAD08" Date: Tue, 28 Sep 2021 18:42:15 +0200 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.7\)) Sent to CCL by: "Marcel Swart (GMail)" [marcel.swart[*]gmail.com] --Apple-Mail=_60EC4447-C83B-4BDC-891F-F58E70EDAD08 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=utf-8 Do a PES scan, going from the reactants to products. The highest point = along the scan should be a good approximation for the barrier, if you = have chosen the step sizes along the PES sufficiently small (I usually = do steps of 0.05 Angs). MS > On 28 Sep 2021, at 14:30, Sumangla Arora arorasumangla%gmail.com = wrote: >=20 >=20 > Sent to CCL by: "Sumangla Arora" [arorasumangla*_*gmail.com] > Dear All, > I am having difficulty getting a transition state between two = intermediates.=20 > When I run a guess structure, I got one imaginary mode. However, when = I put=20 > this structure for OPTTS in orca, this structure is immediately = converting into=20 > the product. To me, this transition state is barrier less. > How can I find this transition state? or > If suppose there is no transition state then how can I prove that? Marcel Swart ICREA Research Professor at University of Girona Director of Institut de Qu=C3=ADmica Computacional i Cat=C3=A0lisi Univ. Girona, Campus Montilivi (Ci=C3=A8ncies) c/ M.A. Capmany 69 17003 Girona, Spain www.marcelswart.eu marcel.swart~!~gmail.com vCard addressbook://www.marcelswart.eu/MSwart.vcf = --Apple-Mail=_60EC4447-C83B-4BDC-891F-F58E70EDAD08 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=utf-8 Do = a PES scan, going from the reactants to products. The highest point = along the scan should be a good approximation for the barrier, if you = have chosen the step sizes along the PES sufficiently small (I usually = do steps of 0.05 Angs).

MS

On 28 Sep 2021, at 14:30, Sumangla Arora = arorasumangla%gmail.com = <owner-chemistry~!~ccl.net> wrote:


Sent to CCL by: "Sumangla  Arora" [arorasumangla*_*gmail.com]
Dear = All,
I am having difficulty getting a transition state = between two intermediates.
When I run a guess structure, = I got one imaginary mode. However, when I put
this = structure for OPTTS in orca, this structure is immediately converting = into
the product. To me, this transition state is barrier = less.
How can I find this transition state? or
If suppose there is no transition state then how can I prove = that?

Marcel Swart
ICREA Research = Professor at University of Girona
Director of Institut de Qu=C3=ADmica Computacional = i Cat=C3=A0lisi

Univ. Girona, Campus Montilivi = (Ci=C3=A8ncies)
c/ M.A. = Capmany 69
17003 Girona, Spain

www.marcelswart.eu
marcel.swart~!~gmail.com

vCard
addressbook://www.marcelswart.eu/MSwart.vcf

= --Apple-Mail=_60EC4447-C83B-4BDC-891F-F58E70EDAD08-- From owner-chemistry@ccl.net Tue Sep 28 13:35:00 2021 From: "Herbert Fruchtl herbert.fruchtl===st-andrews.ac.uk" To: CCL Subject: CCL: How to find barrier less transition state Message-Id: <-54461-210928133304-17404-sM40sC/PCYW1VxFyHH6yWg a server.ccl.net> X-Original-From: Herbert Fruchtl Content-Language: en-GB Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=utf-8; format=flowed Date: Tue, 28 Sep 2021 18:32:45 +0100 MIME-Version: 1.0 Sent to CCL by: Herbert Fruchtl [herbert.fruchtl a st-andrews.ac.uk] Hi Sumangla , You may just have a bad guess. ORCA has a few different methods for locating a transition state. If you have an obvious reaction coordinate (mainly one distance, angle or dihedral changing), you can use the method Marcel proposes. It's even automatic in ORCA 5, with the ScanTS keyword. If it's more complex, I would try the Nudged Elastic Band method (I know that one from materials calculations and haven't used it in ORCA, but it's apparently implemented). Herbert On 28/09/2021 13:30, Sumangla Arora arorasumangla%gmail.com wrote: > > Sent to CCL by: "Sumangla Arora" [arorasumangla*_*gmail.com] > Dear All, > I am having difficulty getting a transition state between two intermediates. > When I run a guess structure, I got one imaginary mode. However, when I put > this structure for OPTTS in orca, this structure is immediately converting into > the product. To me, this transition state is barrier less. > How can I find this transition state? or > If suppose there is no transition state then how can I prove that?> > -- Herbert Fruchtl Senior Scientific Computing Officer / HPC Administrator School of Chemistry, IT Services University of St Andrews -- The University of St Andrews is a charity registered in Scotland: No SC013532