QM/MM electrostatic coupling and number of replicas

Frank Uhlig uhlig... at googlemail.com
Fri Mar 16 14:17:27 UTC 2012

Dear CP2k'lers,

I am curious about the QM/MM capabilities of CP2K and would appreciate
some more detailed explanation on the treatment of the coupling
between periodic images.
As I understood, the keyword REPLICA in section


will set the number of replicas included in the real-space part of the
evaluation of the QM/MM interaction and all other periodic replicas of
the MM part (i.e. long-range contribution) will be handled in
reciprocal space. From a technical point of view, what will happen if
one sets REPLICA to 0? Will there be no contribution in the real-space
sum or only the contribution from the original system (i.e. the
non-replicated MM part).

Does, and if so how, this keyword (REPLICA) influence the calculation
of the electrostatic interaction amongst the QM periodic images?

Best regards and thanks in advance,


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