whenever I have incorporated the QST2 or QST3 I got only one TS but I should have gotten 2-3 TSs in Gaussian 09. And how can I be assure that my result is in good agreement?
I've seen that force calcn(e.g. no, always, once, read) has impact in getting error.
And any good website for IRC calculation stuffs in Gaussian 09?
Dear Mr. Verma, QST2 and QST3 will locate only one transition state between reactant and product. if you are using QST2 method you have to give the geometry of reactant and product. the algorithm will search for TS in between the reactant and product.
in case of QST3 you have to give reactant product and guess geometry of transition state.
2 and 3 are not representing the number of transition state. please see the Gaussian manual for detail.
Dear Mr. Verma, QST2 and QST3 will locate only one transition state between reactant and product. if you are using QST2 method you have to give the geometry of reactant and product. the algorithm will search for TS in between the reactant and product.
in case of QST3 you have to give reactant product and guess geometry of transition state.
2 and 3 are not representing the number of transition state. please see the Gaussian manual for detail.
single negative frequency is the characteristic of transition state and further you can verify transition state by IRC calculation. To understand the concept, first try calculation on small molecules at lower level. In my opinion, acetaldehyde vinyl alcohol tautomerism example is the best one to understand the process of locating transition state and to do irc calculation.
Hi Verma, What Neeraj says is exactly what it is regarding your matter.
You can get more information by looking following tutorials.
https://www.youtube.com/watch?v=mZZ6ebi8UxI
https://www.youtube.com/watch?v=qrL_yWkJj-Q
https://www.youtube.com/user/IaNuisha
http://barrett-group.mcgill.ca/tutorials/Gaussian%20tutorial.pdf
I did one IRC calculation for formaldehyde, in which first it converts from trans to cis then separates as CO and H2. then in this case I did use QST3 but this showed error to me and in book this same calculation shows 3 TSs. So where is the error? I am attaching the files of .com and .log. Please see and tell me.
Thanks all
hi,
I will suggest you to first understand the process and then only plan your calculation. first understand what is happening in the reaction chemically, then make your input file for calculation. This is the example discussed in "Exploring chemistry with electronic structure methods" by Foresman and Frisch. Read it carefully and then attempt calculation.
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