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A How to find vibrational frequency for specific bond? (DFT)

  1. May 5, 2016 #1
    I performed an optimization and frequency calculation at the ub3lyp 6-311g level of theory. The compound has the formula C39H41PS2. Using Molden, I am having a hard time identifying the frequency corresponding to the stretching of a phosphorus carbon double bond present in the molecule. I expect the frequency to be very low in intensity which makes my task harder. I am wondering if there is any way to obtain this information directly from the output file without having to click every frequency on Molden. Thank you very much.
  2. jcsd
  3. May 10, 2016 #2


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    The calculation does not give you a value for the stretching of only this bond. Rather this stretching will contribute to several normal modes. Looking at the output of your calculation, you should see a list of the normal vibrations and the contribution of the individual atoms. Identify those normal modes where the C and P atom in question make a large contribution.
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