I have run 1 ps (pico-second) simulation for formaldehyde using ADMP as implemented in gaussian 09. I got periodic association and dissociation of bonds and structure. The potential energy were also changing periodically like sine graph. I have got similar result for benzene too. The molecules (benzene and formaldehyde) are stable and they should have been stable in Molecular dynamics. Why the bonds are breaking? Is the ADMP results reliable in predicting the stability and time evolution of a structure? Experts please answer.
Travis Pollard. Thanks for the answer. I have understood the problem and solved it. Actually there was some problem in my input. Right now benzene is absolutely stable in BOMD. In my playing around with ADMP and BOMD I found that BOMD is more reliable in checking the stability of a structure.
I'd say, optimization of structure followed by its vibrational analysis is the best way to check stability. If at all you wish to use MD to do so, try simulating the microcanonical ensemble. For a stable/optimized structure, the Kinetic/Potential energy should not vary with time.
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