Relative Energy vs. Reaction Pathway

[Dipankar Saha]

Hello,

How can we plot 'Relative Energy' vs. 'Reaction Pathway' using ATK? Do you have any tutorial available ?

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Dipankar Saha

[Ulrik G. Vej-Hansen]

Sounds like you want the NEB method? We have several tutorials, this one is probably the best introduction: https://docs.quantumwise.com/tutorials/neb_pt/neb_pt.html

[Dipankar Saha]

Okay... Thank you Ulrik !

[Dipankar Saha]

1) Can it show the activation barrier during any surface-site reaction ?
2) How to deduce the thermodynamical (/or, kinetic) stability  of such reactions?

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Dipankar

[Ulrik G. Vej-Hansen]

1) Yes, the NEB methodology can find the energy barrier for any process that is contingent on one or more atoms moving in a constrained way from one stable state to another. It is usually the method of choice for finding energy barriers during chemical reactions. For more details, I suggest you consult the original references.

1) + 2) In general, simple energy considerations work well, but usually it is also necessary to include other contributions to the free energy. For more information, I will suggest you study the work of e.g. H. Jonsson, J. K. Nørskov, K. Reuter, M. Neurock and others.

[Dipankar Saha]

NEB methodology can find the energy barrier for any process that is contingent on one or more atoms moving in a constrained way from one stable state to another.

1) Do you employ the harmonic approximation to TST (transition state theory) ?
How the entropic effects are included?

2) What is a 'dividing surface'?
 

[Ulrik G. Vej-Hansen]

1) Yes, in the HTST object: https://docs.quantumwise.com/manual/Types/HTSTEvent/HTSTEvent.html

2) It is the surface that divides the product and reactant states from each other, and in principle transitions between the two states can happen at any point on it. However, it is (almost) never used in practice, as there usually is a saddle point where the energy is lowest and which will then dominate the rate.

[Dipankar Saha]

Okay, I understand...

Thank you for all the information !!

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Dipankar