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I am a big fan of Mopac (Though I have a very little knowledge about the tool). I have some queries regarding some calculations in Mopac2016:

Problem:

How to calculate Bond or Angle or Dihedral force constant for Vanadium (V) (with other elements: Oxygen and Chlorine)?

My compound (smiliar to): CN(OV(=O)ON(C)C(C)=O)C(C)=O

Structure: enter image description here

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    $\begingroup$ I am not sure I understand your question correctly: Do you wish to calculate a force constant using a method in Mopac, such as PM7? $\endgroup$ – TAR86 Jun 27 '17 at 12:58
  • $\begingroup$ yes. I need the method to calculate the force constants using Mopac2016. $\endgroup$ – Devashish Das Jun 27 '17 at 13:23
  • $\begingroup$ It should be possible to perform a "FORCE" calculation, visualize the resulting vibrational modes and extract the force constant from the appropriate frequency. Note that you need a well-converged geometry for this, preferably without negative frequencies. $\endgroup$ – TAR86 Jun 27 '17 at 16:46
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    $\begingroup$ [1] and [2] provide you with two CIF files (all distances and angles are present) of chloro-oxo-bis(N-phenylbenzylhydroxamato-O,O')-vanadium(V), replace phenyl groups with protons and you have perfect starting geometry. [1]: onlinelibrary.wiley.com/doi/10.1002/cber.19891220205/abstract [2]: sciencedirect.com/science/article/pii/S1381116904002961 $\endgroup$ – andselisk Jun 28 '17 at 0:46
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    $\begingroup$ Finally found it! SEMINAR10, JORGE M. "Calculation of intramolecular force fields from second-derivative tensors." (1996). compbio.chemistry.uq.edu.au/mediawiki/upload/2/2a/… $\endgroup$ – Devashish Das Jul 1 '17 at 20:53

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