[CP2K-user] [CP2K:18549] Re: Cutoff convergence for SCAN functional

[Fabian]

Dear Rajorshi,

The original SCAN functional is known to be very sensitive to the 
integration grid used during calculation. 
An easy fix would be to switch to r2SCAN (acs.jpclett.0c02405) instead: 

      &XC
        &XC_FUNCTIONAL
          &MGGA_X_R2SCAN
          &END
          &MGGA_C_R2SCAN
          &END
        &END
      &END XC

Typically, the cutoff should be converged at 1200Ry with SCAN.

Kind regards,
Fabian
Rajorshi Chattopadhyay schrieb am Freitag, 17. März 2023 um 00:11:52 UTC+1:

> Dear all,
>
> I am trying to do cutoff convergence with the SCAN functional in a aqueous 
> H2O-H2SO4 system. I need an energy convergence of 10**-6 Ha or lower. 
> However, I find that even at a cutoff of 4000Ry (REL_CUTOFF:60), energy 
> convergence is only 10**-4 Ha. The input script is as follows:
>
> &GLOBAL
>
>     PROJECT Sulphate_amb_dens
>
>     RUN_TYPE ENERGY_FORCE
>
>     PRINT_LEVEL MEDIUM
>
> &END GLOBAL
>
> &FORCE_EVAL
>
> &DFT
>
>       MULTIPLICITY 1
>
>       BASIS_SET_FILE_NAME ./BASIS_MOLOPT
>
>       POTENTIAL_FILE_NAME ./SCAN_POTENTIALS
>
>   &MGRID
>
>       CUTOFF 3800
>
>       REL_CUTOFF 60
>
>       NGRIDS 4
>
>   &END MGRID
>
>   &SCF
>
>      SCF_GUESS ATOMIC
>
>      MAX_SCF 3000
>
>      EPS_SCF 1.00000000E-007
>
>      &OT
>
>         MINIMIZER DIIS
>
>         PRECONDITIONER FULL_SINGLE_INVERSE
>
>      &END OT
>
>   &END SCF
>
>   &XC
>
>      &XC_FUNCTIONAL
>
>          &LIBXC
>
>           FUNCTIONAL MGGA_X_SCAN
>
>          &END LIBXC
>
>          &LIBXC
>
>            FUNCTIONAL MGGA_C_SCAN
>
>            &END LIBXC
>
>      &END XC_FUNCTIONAL
>
>     &END XC
>
>    &END DFT
>
>   &SUBSYS
>
>     &TOPOLOGY
>
>      &CENTER_COORDINATES TRUE
>
>      &END CENTER_COORDINATES
>
>     &END TOPOLOGY
>
>
>     &CELL
>
>        ABC 12.32 12.32 12.32
>
>        PERIODIC XYZ
>
>     &END CELL
>
>     &COORD
>
>       @include ../coord_eql
>
>    &END COORD
>
>    &KIND H
>
>       BASIS_SET DZVP-MOLOPT-SR-GTH
>
>       POTENTIAL GTH-SCAN-q1
>
>    &END
>
>    &KIND O
>
>       BASIS_SET DZVP-MOLOPT-SR-GTH
>
>       POTENTIAL GTH-SCAN-q6 
>
>    &END
>
>   &KIND S
>
>       BASIS_SET DZVP-MOLOPT-GTH
>
>       POTENTIAL GTH-SCAN-q6
>
>    &END
>
>
>   &END SUBSYS
>
>  &END FORCE_EVAL
>
>
> I use the pseudopotentials provided by Dr. Joerg Hutter in his github.
>
> Am I missing something in the input script ? Is it possible to achieve 
> such tight energy convergences using SCAN the functional?
>
> I thank you in advance for your help/suggestions. 
>
> -- 
> With Regards,
> Rajorshi Chattopadhyay,
> PhD Researcher in Mineralogy/Crystallography,
> Institut für Geologie und Mineralogie,
> Universität zu Köln, Germany
>
>

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