Hi Matthew,
Based on my understanding, the negative force constant is usually due to that the bond recognition was not correct, there might be a mismatch of the fchk file and the PDB file in terms of the atom sequence.
Pengfei
> On Nov 17, 2023, at 2:51 AM, Matthew Guberman-Pfeffer <matthew.guberman-pfeffer.uconn.edu> wrote:
>
> Dear Amber community,
>
> MCPB reported a negative angle force constant in the second modeling step, even through all the frequencies in the Gaussian calculation were positive.
>
> MCPB set the negative force constant to zero. My questions are: Why did I get a negative force constant? Are the parameters not trustworthy? What could I do to fix this issue?
>
> Best,
> Matthew
>
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Received on Fri Nov 17 2023 - 12:30:02 PST
