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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: n48102 on December 18, 2020, 06:27:03 PM

Title: Calculating transition state in Gaussian
Post by: n48102 on December 18, 2020, 06:27:03 PM

Hi all,

I am relatively new to Gaussian, and am attempting to calculate the transition state for a simple cis to trans isomerization reaction--no catalyst, no solvent. I have not had any luck with the opt=ts approach or the QST2 algorithm. I would have tried using the QST3 algorithm, but I cannot seem to generate a reasonable TS guess (that is, a structure with one negative force constant) to input along with the cis and trans conformer. Any tips are greatly appreciated!

Title: Re: Calculating transition state in Gaussian
Post by: mikeB on January 19, 2021, 06:50:25 PM

Maybe you should do the relax scan for the angle defined by the double bond and substituent you move from cis to trans configuration? Use the structure at the maximum as your guess for the TS.