[CP2K-user] QMM energy conservation problem

Бранислав Миловановић dr.bra... at gmail.com
Tue Nov 24 17:26:46 UTC 2020

Dear cp2k users/developers,

I'm trying to simulate guanine DNA guanine quadruplex using QMMM approach. 
MM force field parameters are prepared with AmberTools20. QM part is 
constituted of Na+ cation coordinated by 8 guanine molecules (so called 
G-octet), while other nucleobases, counterions and solvating water 
molecules are treated with MM.

System was previously equlibrated with NVT ensemble and MM approach with no 
problem encountered. Also, when I try to run QM part of the system only 
using same DFT settings as in the case of QMMM calculation I have no 

However, when I try to run QMMM calculation under present setup (all input 
files in the attachment) I constantly get shift of the Cons Qty during my 
run, for both NVE and NVT runs (graphs from my last attempt are in the 
attachment - last 500fs).

I tried different calculation setup (different timestep, ewald summation 
parms etc.) by looking to the previous topics here in the group but with no 

Maybe there is something trivial bothering me here, qmmm link or similar...
I used IMOMM method for the link and also distributed charges across 
neighbouring MM atoms to neutralize MM subsystem.

Can anybody help me with this?

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