[CP2K-user] [CP2K:20775] Re: SCF Convergence Issues with OT and Diagonalization for CZTS System (Vacuum, Sulfur Layer, and Hydrogen Passivation

[L Heidarizadeh]

Hi,
  Thank you for the suggestion! I’ve already tested the *bulk CZTS system* 
with the same *basis sets, pseudopotentials, and exchange-correlation 
functional*, and it *converged successfully*. However, the *convergence 
problem arises only after introducing the 20 Å vacuum layer* and *surface 
modifications*. I've Adjusted *MAX_SCF* values (up to 500 iterations) and 
tried various *mixing parameters*, including Broyden mixing, but no 
improvement. I have attached my input file for more clarification (before 
switching to OT).
Thank you again for your help and suggestions!
Best regards,
Layla

On Wednesday, October 16, 2024 at 2:15:52 PM UTC-4 Marcella Iannuzzi wrote:

>
> Hi ..
>
> Maybe it simply needs to run for more iterations to converge.
> With the information you provide it is hard to guess.
> Is the electronic structure calculation of the bulk working fine?
> Can you reproduce with your settings (BS, PP, XC etc) the known bulk 
> properties?
>
> Regards
> Marcella
>
>
>
> On Wednesday, October 16, 2024 at 7:40:32 PM UTC+2 lheid... at gmail.com 
> wrote:
>
>> Hello CP2K community,
>>
>> I am running molecular dynamics (MD) simulations on a *Cu2ZnSnS4 (CZTS)* 
>> system using *DFT* in CP2K. Below is a detailed description of my system 
>> and the modifications I applied, followed by the SCF convergence issue I am 
>> facing.
>>
>> Cu2ZnSnS4 (CZTS) system modeled in a periodic box.
>> Unit cell dimensions: 10.8 × 10.8 × 10.8 Å.
>> The goal is to study surface interactions and electronic properties with 
>> a vacuum layer.
>>
>> A 20 Å vacuum layer was added in the Z direction to simulate surface 
>> effects: 10.8 × 10.8 × 30.8 Å
>>
>> A layer of sulfur (S) atoms was added to the surface to stabilize the 
>> system and account for surface states.
>>
>> I attempted hydrogen passivation by capping the dangling bonds with H 
>> atoms to further stabilize the surface.
>> I tried running the SCF loop with and without hydrogen passivation, but 
>> both cases failed to converge.
>>
>> SCF Settings and Methods Tried:
>> *Orbital Transformation (OT):*
>> MINIMIZER: DIIS
>> PRECONDITIONER: FULL_SINGLE_INVERSE
>> ENERGY_GAP: 0.001
>> N_HISTORY_VEC: 7
>> *Diagonalization:*
>> I disabled the OT section and enabled diagonalization as a fallback 
>> method, but the SCF still did not converge. ( I tried different parameters 
>> setting)
>> SCF Parameters:
>> SCF_GUESS: ATOMIC
>> EPS_SCF: 1.0E-6
>> MAX_SCF: 100
>>
>> *The SCF loop exits after a few minutes, failing to converge under both 
>> OT and diagonalization methods.*
>> Are there specific SCF settings or preconditioners that can improve 
>> convergence for systems with large vacuum gaps?
>> Are there alternative strategies for handling surfaces and vacuum layers 
>> that could make the system more stable for electronic structure 
>> calculations?
>> Has anyone successfully applied hydrogen passivation to stabilize 
>> surfaces and improve SCF convergence in CP2K?
>>
>> Any suggestions or advice would be greatly appreciated!
>>
>> Thank you for your help and support.
>>
>>
>>

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&GLOBAL
   PRINT_LEVEL MEDIUM
   PROJECT_NAME CZTS-MD
   RUN_TYPE MD
&END GLOBAL

&FORCE_EVAL
  METHOD QS
  &DFT
    UKS .TRUE.
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME POTENTIAL 
    &MGRID
      NGRIDS 12
      CUTOFF 300
      REL_CUTOFF 50
    &END MGRID
    &QS
      METHOD GPW
      EPS_DEFAULT 1.000E-14
    &END QS
    &POISSON
      PERIODIC XYZ
      PSOLVER PERIODIC
    &END POISSON

    &SCF
      SCF_GUESS ATOMIC
      EPS_SCF 1.0E-6
      MAX_SCF 500  ! Increased iterations

      &DIAGONALIZATION
        ON  ! Using diagonalization method
      &END DIAGONALIZATION

      &MIXING
        ALPHA 0.1
        BETA 0.1
        METHOD BROYDEN_MIXING
      &END MIXING
    &END SCF

    &XC
      &XC_FUNCTIONAL
         &PBE
         &END PBE
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
         POTENTIAL_TYPE PAIR_POTENTIAL
         &PAIR_POTENTIAL
            PARAMETER_FILE_NAME dftd3.dat
            TYPE DFTD3
            REFERENCE_FUNCTIONAL PBE
            R_CUTOFF [angstrom] 16
         &END PAIR_POTENTIAL
      &END VDW_POTENTIAL
    &END XC

    &PRINT
      &MULLIKEN OFF
      &END MULLIKEN
      &HIRSHFELD OFF
      &END HIRSHFELD
    &END PRINT
  &END DFT

  &SUBSYS
    &CELL
      A 10.8683996201 0.0000000000 0.0000000000
      B 0.0000000000 10.8683996201 0.0000000000
      C 0.0000000000 0.0000000000 30.8495998383
      PERIODIC XYZ
    &END CELL

    &TOPOLOGY
      COORD_FILE_NAME coords.xyz  ! Coordinate file name anonymized
      COORD_FILE_FORMAT XYZ
    &END TOPOLOGY

    &KIND Zn
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q12
    &END KIND
    &KIND Sn
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q4
    &END KIND
    &KIND S
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q6
    &END KIND
    &KIND Cu
      BASIS_SET DZVP-MOLOPT-SR-GTH
      POTENTIAL GTH-PBE-q11
    &END KIND
    ! &KIND H
    !   BASIS_SET DZVP-MOLOPT-GTH
    !   POTENTIAL GTH-PBE
    ! &END KIND
  &END SUBSYS
&END FORCE_EVAL

&MOTION
  &MD
    ENSEMBLE NVT
    TEMPERATURE [K] 300
    TIMESTEP [fs] 1.0
    STEPS 5000
    &THERMOSTAT
      REGION GLOBAL
      TYPE CSVR
      &CSVR
        TIMECON 20
      &END CSVR
    &END THERMOSTAT
  &END MD

  &PRINT
    &TRAJECTORY
      &EACH
        MD 1
      &END EACH
    &END TRAJECTORY
    &VELOCITIES ON
    &END VELOCITIES
    &FORCES ON
    &END FORCES
    &RESTART
      BACKUP_COPIES 1
      &EACH
        MD 1
      &END EACH
    &END RESTART
  &END PRINT
&END MOTION