[gmx-users] Bond force constant for GROMOS

[Rausch, Felix]

Dear Gromacs-users,
 
I would like to add a new bond type to the ffbonded.itp of the Gromos53a6 force field. For that, I tried to obtain the force constant for my new bond by performing vibrational frequency calculations with Gaussian. With that, I obtained the force constant in mDyne/A.
My problem is now: How can I convert this value to kJ/(mol*nm(4)) as required for the force field? I already tried, but I only end up at kJ/(mol*nm(2)). Also arround the web I could only find a factor for conversion of mDyne/A to kJ/(mol*nm(2)). Is there any trick or hint you can give me about that?
 
Thanks for your help,
Felix
  
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