[CP2K-user] modelling protein crystals

[Pierre-André Cazade]

Dear CP2K users,

Aside for my previous post, I am also interested in using CP2K to model 
protein crystals. Some of the proteins I am interested in are 
metalloproteins. Using again my test system, beta glycine, I am simply 
adding the following block to an input that works to preform a CELL_OPT. 
Please find part of this input below:

 &FORCE_EVAL
   METHOD  QS
   STRESS_TENSOR  ANALYTICAL
   &DFT
     BASIS_SET_FILE_NAME /usr/local/src/cp2k/data/GTH_BASIS_SETS
     POTENTIAL_FILE_NAME /usr/local/src/cp2k/data/GTH_POTENTIALS
     MULTIPLICITY  0
     CHARGE  0
     &SCF
       MAX_SCF  20
       EPS_SCF  1.e-7
       SCF_GUESS  ATOMIC
       &OT  T
         MINIMIZER CG
         PRECONDITIONER FULL_SINGLE_INVERSE
       &END OT
       &OUTER_SCF  T
         EPS_SCF  1.e-6
         MAX_SCF  50
       &END OUTER_SCF
     &END SCF
     &QS
       LS_SCF T
       EPS_DEFAULT     1.0000000000000000E-10
       EPS_PGF_ORB     1.0000000000000000E-08
       METHOD  GPW
     &END QS
     &MGRID
       NGRIDS  4
       CUTOFF     5.0000000000000000E+02
       REL_CUTOFF     8.0000000000000000E+01
     &END MGRID
     &XC
       DENSITY_CUTOFF     1.0000000000000000E-10
       GRADIENT_CUTOFF     1.0000000000000000E-10
       TAU_CUTOFF     1.0000000000000000E-10
       &XC_FUNCTIONAL  NO_SHORTCUT
         &PBE  T
         &END PBE
       &END XC_FUNCTIONAL
     &END XC
     &POISSON
       POISSON_SOLVER  PERIODIC
       PERIODIC  XYZ
     &END POISSON
   &END DFT

So I tried to add this block:

     &LS_SCF
       PURIFICATION_METHOD TRS4
       EPS_FILTER 1E-6  
       EPS_SCF    1E-7
       MAX_SCF    20
       S_PRECONDITIONER ATOMIC
     &END

and it does not work. Then, I tried:

     &LS_SCF
       PURIFICATION_METHOD TRS4
       EPS_FILTER 1E-6  
       EPS_SCF    1E-7
       MAX_SCF    30
       S_PRECONDITIONER NONE
       &CURVY_STEPS
       &END CURVY_STEPS
     &END

And again, it failed. In both cases, at first the optimization goes well, I 
reach a point where the system is almost optimized and then everything goes 
wrong. If anyone can tell me what I am doing wrong, I would be grateful. 
More generally, if anyone could tell me which algorithms I should use to 
maximize the efficiency of the calculation for large systems (up to about 
100000 atoms), while having decent accuracy and stability, I would be 
grateful. I have checked the various options in SCF, OT, OUTER_SCF, LS_SCF 
and MOTION, but it is unclear which ones are the most suitable and can work 
well together.

Thank you,
Pierre

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