[AMBER] antechamber convergence problem.

From: Vatsal Purohit <vatsal.purohit15.gmail.com>
Date: Mon, 24 Apr 2017 16:32:52 -0400

Hello,

I am trying to run an antechamber program on a ligand pdb file and getting
the following error:
QMMM: Unable to achieve self consistency to the tolerances specified
QMMM: No convergence in SCF after 1000 steps.

Unfortunately, I cannot share my ligand pdb but the ligand is a -4 anion
that has been modified by adding an additional functional group to one of
the oxygens in pymol using the builder feature. The original molecule
before the modification is from a pdb and so reasonably geometry and charge
optimized, I'm guessing.

Due to the instability of the -4 anion in gas phase, only a part of the
molecule (after the phosphate region) was geometry and charge optimized
using gaussian and then attached back to the remaining part of the original
molecule using pymol.

I tried to generate a mol2 file with this modified ligand using antechamber
and got that error. This method has worked for other ligands but with this
one I've been having problems. I have tried to change the value of scfconv
to 1.d-8, tight_p_conv to 0 and grms_tol to 0.002 and have still gotten the
same error.
I tried to use acdoctor and could not identify any other problems with my
molecule.

Could you offer any suggestions on what else I can do to obtain a mol2 file
through antechamber? Thanks in advance.

Regards,
Vatsal
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Received on Mon Apr 24 2017 - 14:00:02 PDT
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