[CP2K-user] [CP2K:17507] Re: Carbon Nitride cell optimization not converging

shreya singh shrsingh183 at gmail.com
Wed Aug 17 16:43:24 UTC 2022


Dear Marcella and Xavier,
Thanks for you suggestions. I have tried Xavier's suggestion exactly as as 
shown above with BFGS. Unfortunately, I observed the same issue (large 
energy fluctuations, large forces and pressure and non-convergence of SCF 
at each optimization step). I have attached the detailed input and output 
files.
AIso, as per Marcella's suggestion  I am trying some settings that allow 
the convergence of the single point calculation for the initial structure. 
The following settings works for SCF convergence *but initial forces are 
still very high*. I am trying optimization with these settings.

  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME POTENTIAL
    CHARGE 0
    MULTIPLICITY 1
    &MGRID
      CUTOFF 600
      REL_CUTOFF 60
      NGRIDS 5
    &END MGRID
    &KPOINTS
      SCHEME MONKHORST-PACK 2 2 4
      !SYMMETRY .TRUE.
    &END KPOINTS
    &QS
      METHOD GPW
      EPS_DEFAULT 1.0E-10
    &END QS
    &POISSON
      PERIODIC XYZ
    &END
    &SCF
      EPS_SCF 5.0E-8
      SCF_GUESS RESTART
      MAX_SCF 20
      &OUTER_SCF
        EPS_SCF 5.0E-8
        MAX_SCF 20
      &END
     &MIXING
       METHOD BROYDEN_MIXING
     &END MIXING
    &END SCF
    &XC
      &XC_FUNCTIONAL PBE
      &END XC_FUNCTIONAL
      &VDW_POTENTIAL
         POTENTIAL_TYPE PAIR_POTENTIAL
         &PAIR_POTENTIAL
            TYPE DFTD2
            REFERENCE_FUNCTIONAL PBE
            R_CUTOFF [angstrom] 15.0
         &END
      &END VDW_POTENTIAL
    &END XC
  &END DFT

and following basis set/ pseudopotentials.
    &KIND C
      ELEMENT   C
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-NLCC-PBE-q4
    &END KIND
    &KIND N
      ELEMENT   N
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-NLCC-PBE-q5
    &END KIND
    &KIND H
      ELEMENT   H
      BASIS_SET DZVP-MOLOPT-GTH
      POTENTIAL GTH-NLCC-PBE-q1
    &END KIND

Any suggestions with this regard will be highly appreciated.
Thanks
Shreya
Email: shrsingh183 at gmail.com
On Tuesday, August 16, 2022 at 11:03:04 PM UTC+5:30 jazz... at gmail.com wrote:

> Hi,
>
> The main issue is the mixing algorithm. Change to Broyden.
> Then you could consider the MOLOPT basis sets.
> Also, "c" parameter is a bit small, I would recommend using k-points, al 
> least "1 1 2" grid mesh.
> NGRIDS 12 is less efficient than NGRIDS 5
> Grimme D2 or D3, see the resulting lattice parameters and volume. What's 
> best for your goal?
>
> What works here:
> ...
>   &DFT
>     BASIS_SET_FILE_NAME BASIS_MOLOPT
>     POTENTIAL_FILE_NAME POTENTIAL
>     CHARGE 0
>     MULTIPLICITY 1
>     &MGRID
>       CUTOFF 600
>       !REL_CUTOFF 60
>       NGRIDS 5
>     &END MGRID
>     &KPOINTS
>       SCHEME MONKHORST-PACK 1 1 2
>       !SYMMETRY .TRUE.
>     &END KPOINTS
>     &QS
>       METHOD GPW
>       EPS_DEFAULT 1.0E-10
>     &END QS
>     &POISSON
>       PERIODIC XYZ
>     &END
>     &SCF
>       EPS_SCF 1.0E-8
>       SCF_GUESS ATOMIC
>       MAX_SCF 250
>      &MIXING
>        METHOD BROYDEN_MIXING
>      &END MIXING
>     &END SCF
>     &XC
>       &XC_FUNCTIONAL PBE
>       &END XC_FUNCTIONAL
>       &VDW_POTENTIAL
>          POTENTIAL_TYPE PAIR_POTENTIAL
>          &PAIR_POTENTIAL
>             TYPE DFTD2
>             !PARAMETER_FILE_NAME dftd3.dat
>             REFERENCE_FUNCTIONAL PBE
>             R_CUTOFF [angstrom] 15.0
>             !&PRINT_DFTD
>             !&END
>          &END
>       &END VDW_POTENTIAL
>     &END XC
>   &END DFT
> ...
>     &KIND C
>       BASIS_SET DZVP-MOLOPT-GTH
>       POTENTIAL GTH-NLCC-PBE-q4
>     &END KIND
>     &KIND H
>       BASIS_SET DZVP-MOLOPT-GTH
>       POTENTIAL GTH-NLCC-PBE-q1
>     &END KIND
>     &KIND N
>       BASIS_SET DZVP-MOLOPT-GTH
>       POTENTIAL GTH-NLCC-PBE-q5
>     &END KIND
> ...
>
> Best,
> Xavier
>
> On Tuesday, August 16, 2022 at 11:39:35 AM UTC-5 shrsi... at gmail.com wrote:
>
>> Dear all,
>> I am trying to optimize the crystal structure of carbon nitride  (Unit 
>> cell contains 144 atoms: C48H24N72). I have tried various suggestions 
>> for Basis sets (SZV, DZVP, TZVP), optimization method (CG BFGS, L-BFGS) but 
>> cell-optimization is not converging. Energy is highly fluctuating, 
>> ultimately forces on a set of atoms become very high and pressure deviation 
>> huge. The initial structure is already optimized in FHI-AIMS, and taken 
>> from a reference (
>> https://pubs.acs.org/doi/full/10.1021/acs.chemmater.7b00965).
>> Particularly, I noticed very high forces on Nitrogen atoms that are 
>> involved in Hydrogen-bonding (see attached image of before and after 
>> structure)
>> I have attached one of the CP2K input file, initial geometry and output 
>> file for your reference.
>> Thanks in advance.
>> Shreya
>> Email: shrsi... at gmail.com
>>
>>

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