[CP2K:6382] Performing the reduced QM/MM calculation entirely classically in Adaptive Buffered Fore Mixing

[Noam Bernstein]

Unfortunately, my recollection is that you can't do that. The adbf code is fundamentally built up from the QM/MM routines. My understanding (Teo can correct me) is that you can't have a QM/MM calculation with no QM atoms.  If it were possible, it might be doable to add the capability of force mixing with pure MM.

  Noam

> On Apr 20, 2015, at 7:24 AM, Lauri Himanen <lauri.... at gmail.com> wrote:
> 
> I would like to perform the reduced QM/MM calculation in the adbf scheme entirely classically, but cannot figure out what settings to choose for this in my system.
> 
> Say I have a potassium ion solvated in water and I would like to perform the extended calculation with the ion and some of the surrounding water that is chosen based on R_QM and R_BUF. Because I have the MM parameters for this entire system, I would however like to do the reduced calculation entirely classically. The problem is that when I define the ion as QM, it gets automatically added to the core QM region and the reduced QM/MM calculation now includes the ion resulting in a QM calculation for it. The extended region is however correct.
> 
> The relevant part of the input I'm currently using looks something like this:
> 
>   &QMMM
>     &QM_KIND K
>       MM_INDEX 3001
>     &END QM_KIND
>     &FORCE_MIXING
>       R_CORE 0 0
>       R_QM 3.7 4.1
>       R_BUF 4.0 4.4
>       ...
>     &END FORCE_MIXING
>     ...
>   &END QMMM
> -- 
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