Question about QM/MM PBC calculation

[marci]

Dear Ruibin

The QM box in QMMM is not periodic. 
However, for such a system I would rather suggest a multiple force 
environment strategy, where all the subsystems can be periodic.
I would set-up 3 force environments:
A full system MM
B water QM
C water MM
The total energy is then E_A +E_B -E_C, and the forces on water are F_A + 
F_B -F_C

regards
marcella

On Friday, November 16, 2012 12:22:40 AM UTC+1, Ruibin wrote:
>
> 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

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