[CP2K-user] [CP2K:18109] Re: Not getting correct optimised geometry for Au(111) surface with ligands (BDT or DMBT)

[Marcella Iannuzzi]

Dear Vikash

In the posted input, the k-points are not used. 
If you already used them, try with a denser mesh and with the *MONKHORST-PACK 
scheme.*
I suggest that you test on one configuration (possibly already a bit 
distorted) the effects on energies and forces by changing k-point mesh and 
cutoff.
If energies and forces are not accurate, the geometry will be wrong. 
EPS_SCF 1.0E-07 should be good enough.
OUTER_SCF is used only to reinitialise the preconditioner for the OT 
approach, hence it is useless with the standard diagonalization method.
 3 layers for a Au slab are insufficient and are keen to lead to weird 
 distortions in the lattice. 

Regards
Marcella
 


On Tuesday, November 29, 2022 at 5:58:54 AM UTC+1 vikashkh... at gmail.com 
wrote:

> Thank you, Marcella, 
> I would like to know the exact PW cutoff I can use.
> And yes, I  have used mesh k-points 2 3 1, are these correct, or do I need 
> to take a bigger grid? If yes, what should it be?
> I thought the default tolerance would be okay. If not, then how much 
> tolerance would be enough?
>
> Regards 
> Vikash
> On Monday, November 28, 2022 at 8:17:19 PM UTC+5:30 Marcella Iannuzzi 
> wrote:
>
>> dear Vikash
>>
>> The system is probably too small.
>> To stabilise the Au slab one should use more layers, we use 6.
>> With such small lateral dimension you should use a mesh of k-points. 
>> Moreover, the tolerance for the convergence of the wavefunction is not 
>> very tight  and the PW cutoff seems quite low. 
>>
>> Regards
>> Marcella
>>
>> On Monday, November 28, 2022 at 1:58:13 PM UTC+1 vikashkh... at gmail.com 
>> wrote:
>>
>>> I'm trying to optimize a small unit cell of  Au(111) surface with 
>>> ligands (BDT or DMBT) but I'm not getting the correct optimized geometry.
>>> I'm using Cp2k 8.1 version.
>>> I'm attaching the Input file here, please have a look and suggest to me 
>>> what's wrong with my calculation. 
>>>
>>> &GLOBAL
>>>   PROJECT Au_64_2BDT
>>>   RUN_TYPE GEO_OPT
>>>   PRINT_LEVEL MEDIUM
>>> &END GLOBAL
>>>
>>> &MOTION
>>>   &GEO_OPT
>>>     TYPE MINIMIZATION
>>>     OPTIMIZER BFGS
>>>     MAX_DR    3.00E-03
>>>     MAX_FORCE 4.50E-04
>>>     RMS_DR    1.50E-03
>>>     RMS_FORCE 3.00E-04
>>>     MAX_ITER 3000
>>>   &END GEO_OPT
>>>
>>>   &CONSTRAINT
>>>     &FIXED_ATOMS
>>>       COMPONENTS_TO_FIX XYZ
>>>       LIST 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
>>>     &END FIXED_ATOMS
>>>   &END CONSTRAINT
>>>
>>> &END MOTION
>>>
>>> &FORCE_EVAL
>>>   METHOD QS
>>>
>>>   &DFT
>>>     BASIS_SET_FILE_NAME BASIS_MOLOPT
>>>     POTENTIAL_FILE_NAME GTH_POTENTIALS
>>>
>>>     &QS
>>>       METHOD GPW
>>>       EXTRAPOLATION USE_GUESS
>>>       EPS_DEFAULT 1.0E-10
>>>     &END QS
>>>
>>>     &MGRID
>>>       CUTOFF 350
>>>       NGRIDS 4
>>>       REL_CUTOFF 60
>>>     &END MGRID
>>>
>>>     &SCF
>>>       SCF_GUESS ATOMIC
>>>       EPS_SCF 1.0E-05
>>>       MAX_SCF 200
>>>       ADDED_MOS 10
>>>
>>>       &OUTER_SCF
>>>        EPS_SCF 1.0E-04
>>>        MAX_SCF 200
>>>       &END OUTER_SCF
>>>
>>>       &DIAGONALIZATION T
>>>         ALGORITHM STANDARD
>>>       &END DIAGONALIZATION
>>>
>>>       &SMEAR ON
>>>         METHOD FERMI_DIRAC
>>>         ELECTRONIC_TEMPERATURE [K] 300
>>>       &END SMEAR
>>>
>>>       &MIXING T
>>>         METHOD BROYDEN_MIXING
>>>         ALPHA 0.4
>>>         NBROYDEN 8
>>>       &END MIXING
>>>     &END SCF
>>>
>>>     &XC
>>>       &XC_FUNCTIONAL PBE
>>>       &END XC_FUNCTIONAL
>>>
>>>       &vdW_POTENTIAL
>>>         DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>>>         &PAIR_POTENTIAL
>>>             PARAMETER_FILE_NAME dftd3.dat
>>>             TYPE DFTD3
>>>             REFERENCE_FUNCTIONAL PBE
>>>             R_CUTOFF 25.0
>>>         &END PAIR_POTENTIAL
>>>      &END vdW_POTENTIAL
>>>     &END XC
>>>
>>>     &KPOINTS
>>>       SCHEME GAMMA 1 1 1
>>>       FULL_GRID .TRUE.
>>>       PARALLEL_GROUP_SIZE  0
>>>     &END KPOINTS
>>>
>>>   &END DFT
>>>
>>>   &SUBSYS
>>>     &CELL
>>>       PERIODIC XYZ
>>>       A    17.3099747000000015    0.0000000000000000   
>>>  0.0000000000000000
>>>       B     0.0000000000000000    9.9939184000000001   
>>>  0.0000000000000000
>>>       C     0.0000000000000000    0.0000000000000000   
>>> 30.0000000000000000
>>>     &END CELL
>>>
>>>     &COORD
>>>       @INCLUDE Au_64_2BDT.xyz
>>>     &END COORD
>>>
>>>     &KIND Au
>>>       BASIS_SET DZVP-MOLOPT-SR-GTH
>>>       POTENTIAL GTH-PBE
>>>     &END KIND
>>>     &KIND H
>>>       BASIS_SET DZVP-MOLOPT-GTH
>>>       POTENTIAL GTH-PBE
>>>     &END KIND
>>>     &KIND C
>>>       BASIS_SET DZVP-MOLOPT-GTH
>>>       POTENTIAL GTH-PBE
>>>     &END KIND
>>>     &KIND S
>>>       BASIS_SET DZVP-MOLOPT-GTH
>>>       POTENTIAL GTH-PBE
>>>     &END KIND
>>>   &END SUBSYS
>>> &END FORCE_EVAL
>>>
>>> I'm also attaching the input and output geometry pics. In the input 3rd 
>>> layer of the gold surface is fixed and the above 2 layers optimize above 
>>> each other(which breaks 111 symmetry) which is not expected.
>>> I hope you understand my problem and I expect a solution, earliest 
>>> possible. 
>>>
>>> Regards 
>>> Vikash Khokhar
>>> Indian Institute of Technology, Madras [image: Screenshot from 
>>> 2022-11-28 18-24-10.png][image: Screenshot from 2022-11-28 18-25-47.png]
>>>
>>

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