Re: [AMBER] Issue with DFTB-MD trajectory

From: Perry, Jamin W. <>
Date: Mon, 17 Nov 2014 06:19:05 +0000


Thank you for your response. I took your advice of extensive output from a serial compilation of the code and found a some distortion in the system that appears anomalous and could be a the tell-tell sign of my silent SCF failure. Thank you again.


From: David A Case []
Sent: Tuesday, November 11, 2014 5:56 AM
To: AMBER Mailing List
Subject: Re: [AMBER] Issue with DFTB-MD trajectory

On Sun, Nov 09, 2014, Perry, Jamin W. wrote:
> I am attempting to calculate a QM/MM trajectory with Sander (released
> with Ambertools14) using SCC-DFTB to represent the quantum region.
> The trajectory successfully integrates for about 250 steps and then
> the program appears to hang without exiting or producing any error
> messages. Is anyone familiar with this sort of error? I appreciate any
> assistance that can be offered. My input control file to Sander can be
> found below.

It is certainly possible that the system may come to some configuration where
the SCF procedure no longer converges. Be sure you are running in serial
mode, set ntpr=ntwx=1, and do a short simulation of 500 steps or so (which
will presumably fail around step 250. Examine the energetics and geometry
near the point of failure.

...good luck....dac

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