CCL: Connection of two different forms having different multiplicities

Dear Sumangla,

Yes, Prof. Neese and Prof. Christoph, as per your suggestion, I have done that calculation using Orca 5.0. And I believe the problem in SCF convergence is no more there.

great! We've spent really a lot of development time to significantly improve a lot of the basic features (SCF convergence, grids, Hessians and NMR timings) with ORCA 5. I am happy to hear that our users are now confirming the advantages - it was worth the effort.

On that note: We will host the 7th ORCA user meeting (virtual-only format), in which - for the first time - our users tell about their applications that made use of ORCA. The list of talks is now online: https://orcaforum.kofo.mpg.de/viewtopic.php?f=53&t=8178


I will go through the manual and read about Minimum energy crossing point (MECP), SurfCrossOpt and SurfCrossNumFreq.
Note: SurfCrossOpt and SurfCrossNumFreq are the actual keywords for Minimum energy crossing point optimizations.
In MECP, I have one more query How will I prove that this is the actual MECP between two surfaces? Like in TS search, we can do IRC and say this is the real TS by looking at the connecting intermediate.

For this purpose I suggest to take the MECP optimized structure, and do a regular !Opt on the two distinct surfaces, i.e. in two individual calculations. Alternatively, you can use !IRC %irc Direction down end .

Best regards,

Christoph


Thank you, Prof. Swart, for suggesting and sharing the book will go through it.

Yes, Prof. Antonio, in this, I need to connect two potential energy surfaces.

Thank you Prof. Jarowski for your answer but the language of my question was confusing at that time, sorry for that.

Thanks
Sumangla

On Thu, Dec 2, 2021 at 12:46 PM Sumangla Arora <arorasumangla _ gmail.com> wrote:
Thank you All

Yes, Prof. Neese and Prof. Christoph, as per your suggestion, I have done that calculation using Orca 5.0. And I believe the problem in SCF convergence is no more there.

I will go through the manual and read about Minimum energy crossing point (MECP), SurfCrossOpt and SurfCrossNumFreq.
In MECP, I have one more query How will I prove that this is the actual MECP between two surfaces? Like in TS search, we can do IRC and say this is the real TS by looking at the connecting intermediate.

Thank you, Prof. Swart, for suggesting and sharing the book will go through it.

Yes, Prof. Antonio, in this, I need to connect two potential energy surfaces.

Thank you Prof. Jarowski for your answer but the language of my question was confusing at that time, sorry for that.

Thanks
Sumangla


On Wed, Dec 1, 2021 at 11:06 PM Christoph Riplinger christoph.riplinger()gmail.com <owner-chemistry _ ccl.net> wrote:

Dear Sumangla,

please look for SurfCrossOpt and SurfCrossNumFreq in the ORCA manual.

Best regards,

Christoph


On 01.12.21 11:15, Sumangla Arora arorasumangla**gmail.com wrote:

I am sorry, my question was confusing.
What I meant was:
I need to find a transition state between peroxo (triplet) and oxo (singlet).
However, I am unable to understand how to approach it because the spin surface is changing. I am using Orca-4.2.1 for these calculations.


Thanks
Sumangla


On Wed, Dec 1, 2021 at 1:59 PM Peter Jarowski peterjarowski+*+gmail.com <owner-chemistry]-[ccl.net> wrote:
Hi Sumangla:

Thanks for the question.

What do you mean by 'connect' and what do you want to do? I assume you want a dimer of these two species or a material and you will need to use QM. A triplet and a singlet make a triplet. Thus, this is pretty easy to implement in any QM software package by replacing a '1' somewhere with a '3' and putting both the singlet complex and the triplet complex in the same input file in some configuration.

As an aside, triplet states are often confused with excited states. They are not. An excited state is a non-ground-state for a given spin multiplicity. The triplet manifold has a ground-state computable by simply requesting the triplet-state energy, no excited-state (e.g. Time-dependent DFT) required (although you could use this and get a slightly different answer).

Happy if anyone disagrees as this is a topic of interest to me that I have struggled with.

Best regards,

Peter

On Wed, Dec 1, 2021 at 7:31 AM SUMANGLA ARORA arorasumangla{:}gmail.com <owner-chemistry|*|ccl.net> wrote:

Sent to CCL by: "SUMANGLA  ARORA" [arorasumangla!^!gmail.com]
Dear All,
The Cu2O2 core can exist in two isomeric forms; oxo and peroxo.
Peroxo is triplet whereas oxo is a close shell singlet. How can we connect
these two different forms having different multiplicities?


Thanks
Sumangla


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