Question about QM/MM PBC calculation

[Ruibin Liang]

Dear CP2K group:
     I am new to CP2K and I have a question about QM/MM PBC calculation. I want to simulate water chain inside a carbon nanotube. I  treat the water with QM and the nanotube carbon with MM, and set the length of both QM and MM box to be to be the same as the nanotube length (~30A). However, I noticed that the QM waters, which are restricted by the nanotube to move along the tube axis,  can't pass through the QM box boundary and goes to the neighboring box. It just gives me warning that I need to add wall to the QM box to hold the QM atoms within the boundary. This is not physically meaningful for my system. I need the QM water to freely move along the nanotube axis by crossing the box boundary back and forth. Is there any way to solve this in CP2K? Or should I turn to GROMACS-CPMD or other packages? Any help will be highly appreciated.

Thank you
Best wishes
Ruibin