[CP2K-user] [CP2K:18842] Unreal cell parameters obtained after CELL_OPT

[Diego López]

Thanks a lot for your suggestion Krack. Then, should I use k-points in the 
calculations or this  MULTIPLE_UNIT_CELL option?

Best,
Diego

El miércoles, 24 de mayo de 2023 a las 15:39:06 UTC+2, Krack Matthias 
escribió:

> Without k points, I suggest to try MULTIPLE_UNIT_CELL 
> <https://manual.cp2k.org/cp2k-2023_1-branch/CP2K_INPUT/FORCE_EVAL/SUBSYS/CELL.html#MULTIPLE_UNIT_CELL> 3 
> 3 1, i.e. a 3x3x1 supercell which has to be defined consistently in the 
> &CELL and TOPOLOGY section.
>
>  
>
> *From: *cp... at googlegroups.com <cp... at googlegroups.com> on behalf of 
> Diego López <diego... at gmail.com>
> *Date: *Wednesday, 24 May 2023 at 14:08
> *To: *cp2k <cp... at googlegroups.com>
> *Subject: *[CP2K:18839] Unreal cell parameters obtained after CELL_OPT
>
> Dear all,
>
>  
>
> I have been trying to optimize a unit cell of the 2D semiconductor CrSBr 
> using GPW method implemented in CP2K. The initial cell parameters were a = 
> 3.6 A, b = 4.8 A and c = 25.0 A (obtained from previous calculations with 
> Quantum Espresso and in good agreement with experimental data). After 128 
> optimization cycles the geometry is optimized and the obtained cell 
> parameters were a = 3.64 A and b = 6.60 A, which leads to a meaningless 
> structure since there is no longer a 2D structure. Also the geometry of the 
> unit cell is really distorted. Any suggestions to improve the accuracy of 
> my calculation? Thank you in advanced.
>
>  
>
> I used this input:
>
>  
>
> &GLOBAL
>   PROJECT test2
>   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 7
>     &POISSON                    ! Solver requested for non periodic 
> calculations
>       PERIODIC XYZ
>     &END POISSON
>      &XC
>       &XC_FUNCTIONAL PBE
>       &END XC_FUNCTIONAL
>      &END XC
>     &SCF
>       SCF_GUESS SPARSE
>       MAX_SCF 100
>       &OT
>       PRECONDITIONER FULL_KINETIC
>       MINIMIZER CG
>       &END OT
>       &OUTER_SCF
>        MAX_SCF 50
>       &END
>     &END SCF
>     &MGRID
>       NGRIDS 4
>       CUTOFF 550
>       REL_CUTOFF 90
>     &END MGRID
>     &QS
>        METHOD GPW
>     &END
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 3.601367151 4.818258107 25.0
>       ALPHA_BETA_GAMMA 90 90 90
>       PERIODIC XYZ
>       SYMMETRY ORTHORHOMBIC
>     &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
>     &END
>     &KIND Cr
>       ELEMENT Cr
>       BASIS_SET DZVP-MOLOPT-SR-GTH
>       POTENTIAL GTH-PBE-q14
>       MAGNETIZATION 3.0
>     &END KIND
>     &KIND S
>       ELEMENT S
>       BASIS_SET TZV2P-MOLOPT-GTH
>       POTENTIAL GTH-PBE-q6
>     &END KIND
>     &KIND Br
>       ELEMENT Br
>       BASIS_SET DZVP-MOLOPT-SR-GTH
>       POTENTIAL GTH-PBE-q7
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> &MOTION
>   &CELL_OPT
>     TYPE DIRECT_CELL_OPT
>     MAX_DR    1.0E-03
>     MAX_FORCE 1.0E-03
>     RMS_DR    1.0E-03
>     RMS_FORCE 1.0E-03
>     MAX_ITER 200
>     OPTIMIZER BFGS
>     KEEP_SYMMETRY
>   &END CELL_OPT
>  &GEO_OPT
>     MAX_DR    1.0E-03
>     MAX_FORCE 1.0E-03
>     RMS_DR    1.0E-03
>     RMS_FORCE 1.0E-03
>     OPTIMIZER BFGS
>   &END GEO_OPT
> &END MOTION
>
>  
>
>  
>
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