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Simulating CO2 as a flexible molecule impossible? (MD)

  1. Jan 9, 2010 #1
    Hi there,

    i'm trying to do molecular dynamics simulations with CO2. However, I'm running into some problems, that I don't fully understand up to know.

    From a naive point of view, I would describe CO2 as a linear molecule consisting of 2 C-atoms and 1 O-atom.
    To simulate a flexible model I would specify an equilibrium bond length lC-O, a 180° equilibrium angle O-C-O and the corresponding force constants.
    And that's what I did by taking some well-known CO2 parameter sets. (EPM/EPM2 etc.)

    However the shake-algorithm (responsible for enforcing the bond constraints) in the simulation code does not converge and in the manual of the simulation package I'm using it says:
    So now I'm pretty confused. On the one hand there are many papers simulating flexible oder partially flexible CO2 molecules, but on the other hand there seems to be a principle problem with molecules of this kind.
    Does anyone have an idea on how to resolve these two somewhat contradicting facts?
    Or can explain to me, why it should be impossible like the quotation says?

    Many many thanks in advance
    greetings angu
  2. jcsd
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