I am giving a guess TS for a molecule and optimizing it by modredundant constraint but it does not get converged. I tried QST2 method but the obtained TS is not good,,i mean more than one imaginary frequency come into being. Can anyone tell me some wayout to locate transition state of a reaction.
I would run qst2 and qst3 calculations in gaussview too.. If they crash with a higher basis set, it's better to first do the calculations in a lower basis set (such as 321-G) and once you have a good guess from that, then run a qst3 calculation using your higher basis set.. Good luck..
Asalamu alaikum ADEL,
Is there any other way to locate the transition state of a reaction besides QST2 and QST3.
I always use OPT=(TS, CALCFC, NOEIGEN) keyword in the route section with the best possible initial guess for the transition state. As Malkanthi suggested, it is better to try a smaller basis set if the TS you are looking for is not so common. You may or may not succeed in first few attempts. Look closely at the output file ( or the ongoing calculation) in GaussView to figure out how your guesses are progressing. If it deviates too much from what you are trying to get then modify your initial guess otherwise tweak the intermediate structure (the one closest to your TS) as the new guess. Hope this answer helps you.
Megha,
i am trying it..i will let you know about the success rate
THANKS
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