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Topic: Computational Chem *delete me*  (Read 3898 times)

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gravenewworld

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Computational Chem *delete me*
« on: December 02, 2005, 07:34:22 PM »
Hello everyone, I am the new guy here.  Anyway I came because I am in some need of some computational help for some projects I have been working on.  The reaction I am trying to study is Biphenylene, when introduced to Li2 and ultrasound, opens up to give the biphenyl molecule.  I have been trying, computationally, to figure out how the reaction progresses, i.e. transition states, intermediates, etc. so that I can take all the peices of the the "movie" of this reaction, put them together, and make the movie.  I however, have hit a wall.   First I optimized the biphenylene system with the lithiums above and below the center, which I optimized doing a DFT calc.  I then optimized the dilthiobiphenyl system at DFT, which went to groundstate.  The problem is when I run a QST2 calc in order to find a transition state between them.  The TS I find looks good, but then when I optimize  a point to the "left" of the transition state, it doesn't optimize backdown to the groundstate structure I input.  The structure that it optimizes backdown to, is about 6kcal/mol in energy off the original input optimized structure.  Does anyone know of any tricks that I can do to find a better transition state possibly?  I found a journal article from a guy at yale who did a bunch of calc using a B3LYP/6-31++G** basis set for lithium containing organic compounds.  Is anyone familiar with this basis set?  What kind of results did you get with it?  How much cpu power will it chew up?  Does anyone know of any other calcs beside the QST2 calc that will find transition states between two groundstate structures?

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