Performing the reduced QM/MM calculation entirely classically in Adaptive Buffered Fore Mixing

Lauri Himanen lauri.... at
Mon Apr 20 11:24:52 UTC 2015

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 

    &QM_KIND K
      MM_INDEX 3001
      R_CORE 0 0
      R_QM 3.7 4.1
      R_BUF 4.0 4.4
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