[CP2K-user] [CP2K:11092] convergence of forces in the dynamical QM region as a function of buffer region

[Noam Bernstein]

I'm not sure I follow the question - the force printed out by the &MOTION
section is the "mixed" force.  The force on the MM atoms should be
independent of the buffer radius.  The force on the dynamical QM region
atoms will change as you change the buffer radius, and hopefully approach
some converged value.  I believe that the &PRINT subsection of the
&QMMM&FORCE_MIXING section should print out information as to which atoms
are MM and QM, but I've forgotten the precise syntax, but you can also tell
by seeing which forces vary when you change the buffer radius, and which do
not.

            Noam

        Noam

On Wed, Jan 2, 2019 at 8:44 AM Wei Zhang <zwei88... at gmail.com> wrote:

> Deal all,
> I would like to use the Ad buffer QM/MM method to calculate the free
> energy. And as mentioned in "The adaptive buffered force QM/MM method in
> the CP2K and AMBER software packages." *Journal of Computational
> Chemistry* 36(2015):633-648." "The buffer region size required to reduce
> the force errors at the dynamical boundary below a preset threshold can be
> determined from the convergence of forces in the dynamical QM region as a
> function of buffer region size, carried out separately before the
> production run on a few relevant configurations (e.g., near the estimated
> extrema of a free energy profile). " *Here is my question: How can we get
> the force of the dynamical QM region? I have put force put in the MOTION
> section (&MOTION&MD&PRINT&FORCE), and got the file of **-frc-1.xyz
> <http://frc-1.xyz>. I also put force print in the QMMM FORCE_EVAL section
> (&FORCE_EVAL&PRINT&FORCE), and got the ATOMIC FORCE in [a.u. ] in the
> output file. *
> *How can I calculate the force of the dynamic QM region and how the test
> the convergence of it?*
>
> *Thank you very much for your help.*
>
> *Happy New year.*
>
> *Wei*
>
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