[CP2K-user] [CP2K:18907] Re: Incorrect optimized geometry using CELL_OPT

[Marcella Iannuzzi]

Hi, 

I would start by using better basis sets (e.g., DZVP, TZVP) and increasing 
the PW cutoff 

Regards
Marcella 

On Friday, June 9, 2023 at 1:00:42 PM UTC+2 Diego López wrote:

> Dear CP2K users,
>
> I am kind of new using cp2k but I have been using the software fo a couple 
> of months. I am trying to optimize both geometry and cell parameters of 
> different semiconductor material but the obtained geometries are distorted 
> compared with experimental data or relaxed geometries obtained using 
> Quantum Espresso or VASP. 
>
> My optimized geometries have a lack of symmetry compared with experimental 
> data, i.e. the atoms that should be aligned in an especific axis tend to 
> alternate the positions in the crystal, so my results are no compatible 
> with the expected ones.
>
> Which parameters should I change in my calculations? I tried lowering the 
> EPS_SCF to increase accuracy, increasing the supercell and using larger 
> basis sets but the result does not change. I attatch an example of input 
> that I used for these calculations.
>
> &GLOBAL
>   PROJECT
>   RUN_TYPE CELL_OPT
>   PRINT_LEVEL MEDIUM
> &END GLOBAL
>
> &FORCE_EVAL
>   METHOD Quickstep              ! Electronic structure method (DFT,...)
>   STRESS_TENSOR ANALYTICAL
>   &DFT
>     BASIS_SET_FILE_NAME  BASIS_MOLOPT
>     POTENTIAL_FILE_NAME  GTH_POTENTIALS
>     MULTIPLICITY 301
>     UKS
>     &POISSON                    ! Solver requested for non periodic 
> calculations
>       PERIODIC XYZ
>     &END POISSON
>      &XC
>       &XC_FUNCTIONAL PBE
>        &PBE
>         PARAMETRIZATION PBESOL
>        &END
>       &END XC_FUNCTIONAL
>      &END XC
>     &SCF
>       SCF_GUESS ATOMIC
>       MAX_SCF 40
>       EPS_SCF 3E-06
>       &OT
>       PRECONDITIONER FULL_KINETIC
>       MINIMIZER CG
>       &END OT
>       &OUTER_SCF
>        MAX_SCF 320
>        EPS_SCF 3E-06
>       &END
>     &END SCF
>     &MGRID
>       NGRIDS 4
>       CUTOFF 550
>       REL_CUTOFF 90
>     &END MGRID
>     &QS
>       METHOD GPW
>       EXTRAPOLATION ASPC
>       EPS_DEFAULT 1E-014
>     &END
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 3.601367151 4.818258107 25.0
>       ALPHA_BETA_GAMMA 90 90 90
>       PERIODIC XYZ
>       SYMMETRY ORTHORHOMBIC
>       MULTIPLE_UNIT_CELL 5 5 1
>     &END CELL
>     &TOPOLOGY                    ! Section used to center the atomic 
> coordinates in the given box. Useful for big molecules
>       COORD_FILE_FORMAT xyz
>       COORD_FILE_NAME  ./crsbr.xyz
>       MULTIPLE_UNIT_CELL 5 5 1
>     &END
>     &KIND Cr
>       ELEMENT Cr
>       BASIS_SET SZV-MOLOPT-SR-GTH
>       POTENTIAL GTH-PBE-q14
>       MAGNETIZATION 3.0
>     &END KIND
>     &KIND S
>       ELEMENT S
>       BASIS_SET SZV-MOLOPT-GTH
>       POTENTIAL GTH-PBE-q6
>     &END KIND
>     &KIND Br
>       ELEMENT Br
>       BASIS_SET SZV-MOLOPT-SR-GTH
>       POTENTIAL GTH-PBE-q7
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> &MOTION
>   &CELL_OPT
>     TYPE DIRECT_CELL_OPT
>     MAX_ITER 200
>     OPTIMIZER LBFGS
>     KEEP_SYMMETRY
>   &END CELL_OPT
> &END MOTION
>
> Thanks in advanced
>

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