Re: ABF Non-Uniform Zcount

From: Jérôme Hénin (
Date: Wed Apr 27 2022 - 08:40:35 CDT

Hi Joey,

First I would compare this with the ".count" file, to see if there is any major difference in distribution. If that is the case, this can be helped by a tighter extended system restraint (lower extendedFluctuation parameter). However, I doubt this is the case here.
A likely cause is slow relaxation causing a drift in an orthogonal direction to your chosen reaction coordinate, so that ABF is adapting to a free energy landscape that seems to be changing all the time, which defeats the adaptation process.

My recommendation to troubleshoot this is to analyze the slow coordinates in the ABF trajectory.


----- On Apr 26, 2022, at 6:33 AM, Joey Farrell <> wrote:

> Hello,

> I was wondering if I can get any insights into potential causes of non-uniform
> zcount when running an ABF system. Specifically, my .zcount file has the
> following (abridged) contents:

> 12.05 1233990

> 12.15 1248322

> 12.25 1168793 ...

> 15.75 121013

> 15.85 87096

> 15.95 57720
> Please let me know if this is an issue and, if it is, potential ways to go about
> remedying it. I can provide more configuration information ad hoc.

> Thank you,
> Joey

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