[CP2K-user] QM water molecules tend to accumulate at the borders of the QM cell in periodic QM/MM simulation

[Sal]

The problem seems to be related to the "GEEP" QM/MM coupling as the problem 
doesn't happen with the mechanical coupling. 
I think I'm using correct parameters for GEEP and my DFT settings seem to 
be reasonable too. Does anyone know how to solve this issue?

Thanks,
Sal 







On Thursday, December 6, 2018 at 9:57:42 AM UTC-8, Sal wrote:
>
> Dear CP2K developers,
>
>
> I am running periodic QM/MM simulation (BLYP/TZV2P with GTH-BLYP) that 
> includes water, protein and lipid. 
>
> Problem is that few  water  molecules are pushed against the edge even 
> with a hard quadratic wall (K=40 kcalmol/angstrom^2).
>
> QM cell dimensions are chosen to be ~2 A larger than QM size.
>
> I am  wondering if you know any specific parameter setting (e. g. # of LIB 
> in GEEP, NGRIDS, GPW cutoffs, ...) would cause this.
>
>
>
>
>
> Thanks for your time,
>
> Sal
>
>
>
>
>
> More detail about my QM/MM setup:
>
>
>
>
>     &MGRID 
>
>       COMMENSURATE
>
>       &RS_GRID
>
>         DISTRIBUTION_TYPE DISTRIBUTED
>
>       &END RS_GRID
>
>       CUTOFF 360
>
>       NGRIDS 4
>
>       REL_CUTOFF 60
>
>     &END MGRID                                                      
>
>
>     &QS                                                             
>
>       METHOD GPW                                                      
>
>       EPS_DEFAULT 1.0E-10                                             
>
>       MAP_CONSISTENT TRUE                                           
>
>       EXTRAPOLATION ASPC                                              
>
>       EXTRAPOLATION_ORDER 3                                           
>
>     &END QS                                                         
>
>
>     &SCF                                                            
>
>       MAX_SCF 30 
>
>        EPS_SCF 1.0E-6
>
>       SCF_GUESS RESTART
>
> #      SCF_GUESS ATOMIC
>
>       &OT T
>
>           MINIMIZER DIIS
>
>          N_DIIS 7
>
>       &END OT
>
>       &OUTER_SCF
>
>          MAX_SCF 3
>
>          EPS_SCF 1.0E-6
>
>       &END OUTER_SCF 
>
>
>     &XC                                                            
>
>       &XC_FUNCTIONAL BLYP
>
>       &END XC_FUNCTIONAL
>
>     &VDW_POTENTIAL                                                
>
>          POTENTIAL_TYPE  PAIR_POTENTIAL
>
>          &PAIR_POTENTIAL                                                 
>
>            TYPE  DFTD3
>
>            PARAMETER_FILE_NAME  dftd3.dat
>
>            REFERENCE_FUNCTIONAL BLYP
>
>          &END PAIR_POTENTIAL
>
>        &END VDW_POTENTIAL
>
>     &END XC                                                         
>
>
>       
>
>     
>
> .....
>
> .....
>
> .....
>
>
>    E_COUPL GAUSS
>
>     USE_GEEP_LIB  9
>
>     &PERIODIC 
>
>        GMAX 1.0
>
>        &MULTIPOLE 
>
>           EWALD_PRECISION 1.0E-6
>
> #          NGRIDS  16 16 24
>
>           ANALYTICAL_GTERM 
>
>           RCUT  14.0
>
>        &END MULTIPOLE
>
>     &END PERIODIC
>
>
>     &CELL
>
>       ABC [angstrom] 15 16 22
>
>
>       PERIODIC XYZ 
>
>     &END CELL
>
>     CENTER NEVER
>
>     &WALLS 
>
>       type quadratic
>
>       k [kcalmol/angstrom^2] 40.0
>
>       WALL_SKIN  1.0 1.0 1.0
>
>     &END WALLS 
>
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