Re: [AMBER] antechamber no convergence

From: Jianhui Tian <>
Date: Mon, 16 Sep 2013 15:47:28 -0400

Dear David,

Sorry to bother and take your time again.

The no convergence happens during the sqm calculation for charge.
Is it doable/reasonable to get the topology like this:
1. calculate the topology for the AMP PNP with -2 charge (this charge can
2. get the charges using another way
3. fix the charges in the final topology file
The assumption I have here is the bonded and vdw parameter will not be
affected by the net charge of the ligand.

Otherwise, I do not know how to run the antechamber in a
broke-up/step-by-step way.


On Mon, Sep 16, 2013 at 10:13 AM, case <> wrote:

> On Fri, Sep 13, 2013, Jianhui Tian wrote:
> >
> > Please find in the attachment the PDB of AMPPNP I used. Thanks a lot for
> > your time and your kind help.
> This is a problem that requires more time than I have had so far. It may
> be a
> problem with the initial geometry. What I've found so far is that
> Gaussian09
> also fails with this input, and that PM6 seems OK, and can optimize the
> geometry fine. I've not yet had time to investigate other options; you
> might
> try geometry optimization at the PM6 level, then try using that for AM1
> calculations.
> Of course, in general, using gas-phase calculations for a -4 anion is a
> stretch. You might consider adding a proton and looking at the -3 state,
> since the pKa of ATP is around neutral pH.
> ...dac
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Received on Mon Sep 16 2013 - 13:00:02 PDT
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