Non-integer charge in QM/MM simulation

Pablo Campomanes at
Wed Jan 20 19:39:30 UTC 2010

Dear CP2K users,

While running a QM/MM MD simulation with CP2K, I found the following information concerning the total charge of my MM region:

CHARGE_INFO| Total Charge of the Classical System:                    -0.253321

I was wondering if the non-integer charge is compensated distributing another charge of opposite sign over the MM atoms to achieve the neutrality of the system as done in CPMD... or the user must take care of create such an integer charge, for instance, cutting between the appropriate covalent bonds in the QM/MM region.
I couldn't see any piece of code dealing with this topic in the sources, but I am still not sure...

Could anybody shed light in this issue?

Thank you very much in advance.

Best regards,


Pablo Campomanes
Laboratory of Computational Chemistry and Biochemistry 
BCH 4118 EPF Lausanne

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