Mr. Nikitin,

The answer to your question is that there is a lack of a systematic data correlating between MD computations and experiments on chemical reactivity. Or there is unable to us to see are there real connection with parameters.

Dear Sergey,

Please, check these papers:

Dear Péter Szabó,

Thanks!

Do you know any other existing examples (in the theoretical or experimental regards) of chemical reactinos with higher order saddle points?

Dear Sergey,

Many years ago, I had the same question and I found only those two papers. It is really interesting question.

Dear Péter Szabó ,

I guess current research in this field is performed in Wolfgang Quapp ' s group.

Best regards

Thanks Sergey for remembering to me!

First of all, a monkey is not an SP of index 2.

A monkey is a valley-branching at an SP: so to say index 1+1/2.

(See also below the last remark.)

Second: from a usual SP You can expect to go down into two different

minimums. From an SP of index two You can expect to go down into up to

four different minimums!

(A nice example is currently submitted by me.)

Some Papers:

author ={Heidrich, D. and Quapp, W.},

title ={Saddle points of index 2 on PES and their role in theoretical

reactivity investigations},

journal= {Theor. Chim. Acta},

volume = {70},

pages = {89--98},

year = {1986}

author={Yu G Khait and A I Panin and A S Averyanov},

title= {Search for stationary points of arbitrary index by augmented

{H}essian method},

journal={Int. J. Quant. Chem.},

volume = 54,

year =1994,

pages ={329--336}

author = "Chaudhury, Pinaki and Bhattacharyya, S.P",

journal= "Chemical Physics",

number = "3",

pages = "313--325",

title = "{Locating critical points on

multi-dimensional surfaces by genetic algorithm: test cases including

normal and perturbed argon clusters}",

volume = "241",

year = "1999"

(It determinds also SPs of higher index)

author ={Minyaev, R. M. and Getmanskii, I. V. and Quapp, W.},

journal ={Russ. J. Phys. Chem.},

title ={Ab initio Study of the {NH}$_3$...{H}$_2$ Complex -

First Saddle Point of Index Two on a Reaction Path},

volume ={78},

pages = {1494},

year = {2004}

author = {Ezra, G. S. and Wiggins, S.},

title ={Phase-space geometry and reaction dynamics near index 2 saddles},

journal = {J. Phys. A},

volume = {42},

pages = {205101},

year = {2009}

author ={P. Collins and Ezra, G. S. and Wiggins, S.},

title ={Index k dividing surfaces in phase space with application

to isomerization dynamics},

journal= {J. Chem. Phys},

volume = {134},

pages = {244105},

year = {2011}

author = "Bofill, Josep Maria and Quapp, Wolfgang and Caballero, Marc",

journal= "Chem. Phys. Lett.",

pages = "203--208",

title = "{Locating Transition States on Potential Energy Surfaces by the

Gentlest Ascent Dynamics}",

volume = "583",

year = "2013"

(It has also formulas for SPs of higher index)

AUTHOR = {W. Quapp and J. M. Bofill},

TITLE = {Embedding of the Saddle Point of Index Two on the PES of the

Ring Opening of Cyclobutene},

JOURNAL = {Int. J. Quantum Chem.},

volume = 115,

pages = {1635-1649},

YEAR = 2015

And a higher dimensional imagination of Valley-Ridge Inflection (IVR)

points which usually form a manifold:

author = {Quapp, W.},

title = {Can We Understand the Branching of Reaction Valleys

for more than two Degrees of Freedom?},

journal = "J. Math. Chem.",

volume = {54},

pages = {137-148},

year = "2015"

I hope this is some test to read further... and to understand further.

Kind regards

Wolfgang Quapp

Characterization of an SP_2

-- From a usual SP of index 1 one can expect to go down by the

steepest descent ( SD) into two different minimum valleys using for

the first step the eigenvector to the negative eigenvalue.

-- From an SP of index two one can hope that it is possible to go

down by the SD into up to four different minimums using for the first

step the two eigenvectors to negative eigenvalues.

(But many other cases are possible.)

(The text is in a paper which is in review .)

Hi, check this paper for further meaning of second saddle points.

https://www.sciencedirect.com/science/article/abs/pii/S0022459619304359

In my point of view, it is related with the existence of cuasi -transition state structures in the "reaction path", which can improve o decline the reaction speed and or affects the energetic behavior in general.

You can explore these fact by using synchronous NEB instead of common NEB computations, even with RFO approach to reach the true transition-state structure( both available in classical ( GULP code) and DFT approaches (VASP, CASTEP, QE, etc.)

I cannot get from Elsevier this paper;

they forbitt the download for usual scientists.

Wolfgang

Email me

sci hub

Google it for free paper download