Weird movement of Pt (fcc 111) layers with one OH radical on top

[GENG YUAN]

Dear CP2K users,

I am performing geometry optimizations for Pt slab (fcc111) with one hydroxyl (OH) radical on top. First, the cell optimization of bulk Pt (fcc111) is performed and successfully converged (Pt_cellopt.xyz). 

However, when I put one OH radical on Pt 111 to perform geometry optimization, I observed a weird movement of the top Pt layers although the geo-optimization converged (attached: Pt111_oh.xyz). We fixed the bottom three layers, only allowing the top three layers to relax during optimization. You could see the movement of the top layers of Pt which significantly changes its lattice structure. 

At this point, we doubt whether this output is reasonable. We are thinking that we may be missing something about the settings in the input file but we are running out of ideas.

The input and output files are attached (com.inp, com.out), the original coordinate file is also attached (oricoor_Ptoh.xyz). Any advice is welcome!

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Our input file is also written below for your convenience.

&GLOBAL
  PROJECT com_geo
  RUN_TYPE GEO_OPT
  PRINT_LEVEL LOW
&END GLOBAL
&FORCE_EVAL
  METHOD QS
  &SUBSYS
    &CELL
      ABC 10.608 9.653 23.866
      SYMMETRY ORTHORHOMBIC
    &END CELL
    &TOPOLOGY
     COORD_FILE_NAME ./oricoor_Ptoh.xyz
     COORDINATE xyz
    &END
    &KIND Pt
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q18
    &END KIND
    &KIND H
      BASIS_SET TZV2P-MOLOPT-GTH
      POTENTIAL GTH-PBE-q1
    &END KIND
    &KIND O
      BASIS_SET TZV2P-MOLOPT-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND
  &END SUBSYS
  &DFT
    BASIS_SET_FILE_NAME ./BASIS_MOLOPT
    POTENTIAL_FILE_NAME ./GTH_POTENTIALS
    LSD
    MULTIPLICITY 2
    &QS
      EPS_DEFAULT 1.0E-12
    &END QS
    &MGRID
      CUTOFF 400
      NGRIDS 5
      REL_CUTOFF 40
    &END MGRID
    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-06
      MAX_SCF 200
      ADDED_MOS 100
      &OUTER_SCF
        MAX_SCF 50
        EPS_SCF 1.0E-6
      &END
      &DIAGONALIZATION T
        ALGORITHM STANDARD
      &END DIAGONALIZATION
      &MIXING T
        METHOD BROYDEN_MIXING
        ALPHA 0.1
        NBROYDEN 8
      &END MIXING
      &SMEAR ON
        METHOD FERMI_DIRAC
        ELECTRONIC_TEMPERATURE [K] 500
      &END SMEAR
      &PRINT
        &RESTART ON
        &END RESTART
      &END PRINT
    &END SCF
    &XC
      &XC_FUNCTIONAL
         &LIBXC
           FUNCTIONAL XC_GGA_X_PBE_R
         &END
         &LIBXC
           FUNCTIONAL XC_GGA_C_PBE
         &END
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
         POTENTIAL_TYPE PAIR_POTENTIAL
         &PAIR_POTENTIAL
            LONG_RANGE_CORRECTION
            PARAMETER_FILE_NAME dftd3.dat
            TYPE DFTD3
            REFERENCE_FUNCTIONAL revPBE
         &END PAIR_POTENTIAL
       &END VDW_POTENTIAL
       &XC_GRID
        XC_DERIV NN50_SMOOTH
       &END XC_GRID
    &END XC
  &END DFT
&END FORCE_EVAL
&MOTION
  &GEO_OPT
    TYPE MINIMIZATION
    MAX_DR    1.0E-03
    MAX_FORCE 1.0E-03
    RMS_DR    1.0E-03    
    RMS_FORCE 1.0E-03
    MAX_ITER 500
    OPTIMIZER BFGS
  &END GEO_OPT
  &CONSTRAINT
    &FIXED_ATOMS
      COMPONENTS_TO_FIX XYZ
      LIST 1..48
    &END FIXED_ATOMS
  &END CONSTRAINT
&END MOTION  

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Below are some screenshots showing the weird movement of Pt layers during Geometry optimization.

Many thanks,

Sincerely,

Geng

[Marcella Iannuzzi]

Dear GENG YUAN

I suspect that the lateral size of the slab is too small. 

You probably need to use either a larger model or k-points.

Regards

Marcella

[GENG YUAN]

Dear Marcella,

Many thanks for your suggestion, I will try different sizes of the slab to see.

Sincerely,

Geng