Re: [AMBER] Distorted water molecules in QM partition (possible bug)

From: David A Case <>
Date: Tue, 18 Jan 2022 07:42:33 -0500

On Mon, Jan 17, 2022, Antonio Frances Monerris wrote:
>I am performing QM/MM simulations with Amber 20 and Orca 5.0. I would like
>to report a problem when including water molecules in the QM partition
>using Sander (Amber 20).
>The water molecules inside the QM partition appear with wrong H-O-H angles
>(~70 ) and short O-H distances (~0.7-0.8 A) already in the first frame of
>the QM/MM simulation. The water molecules minimized with MM had correct
>parameters prior to the QM/MM job. This strange water molecule distortions
>are not solved during the QM/MM minimization.

Can you clarify what you mean by "the first frame of the QM/MM simulation"?
Did you do a one- or two-step minimization, and look at the output
coordinates? Try to find the simplest calculation that you can that
illustrates the problem.

QM/MM folks: is there some way to save or otherwise access the Orca input


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Received on Tue Jan 18 2022 - 05:00:02 PST
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