[CP2K-user] [CP2K:20773] SCF Convergence Issues with OT and Diagonalization for CZTS System (Vacuum, Sulfur Layer, and Hydrogen Passivation

[L Heidarizadeh]

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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