[CP2K-user] [CP2K:16253] Re: Improve extrapolation between relaxation steps?

[Matt Watkins]

'so for wide gap insulators you should for sure only need a few SCF cycles 
to converge'
I meant to write when fairly relaxed / close to the minimum ...



On Wednesday, 17 November 2021 at 18:06:33 UTC Matt Watkins wrote:

> Well, CP2K was setup to do Born-Oppenheimer MD for bio systems   - so for 
> wide gap insulators you should for sure only need a few SCF cycles to 
> converge.
>
> Is your  system insulating (band gap, let's say > 0.2 eV)? If not 
> different approach needed.
>
> If so, improve the OT setup  - especially the preconditioner
>
> remove
> PRECONDITIONER FULL_KINETIC
> ENERGY_GAP 0.01
>
> try 
>
> PRECONDITIONER FULL_SINGLE_INVERSE
>
> or (can be expensive for larger systems)
>
> PRECONDITIONER FULL_ALL
>
> and leave out the energy_gap (if you are using an up-to-date cp2k)
>
> Also check that you XC setup is correct ...
>
> Matt
>
>
> On Tuesday, 16 November 2021 at 17:58:59 UTC nwi... at berkeley.edu wrote:
>
>> Hello all, 
>>
>> When I run a relaxation for a complex system, e.g. in my case a defective 
>> transition metal oxide with hybrid dft on a modest ~200 atom supercell, 
>> each SCF still takes quite a long time to converge. 
>>
>> I originally came from vasp before switching to cp2k, and it in that 
>> code, my experience was that once the first scf loop converged, the next 
>> relaxation step would take much less time, and so on until the last few 
>> steps converged in just a few iterations. This isn't my experience with 
>> CP2K though. Running CG on my most recent relaxation I still find that 
>> after more than 20 relaxation steps, 40-50 scf steps are required to 
>> achieve convergence.
>>
>> Is this something that I could improve by changing certain settings? 
>> Below is the relevant info for my input file. Please note that I understand 
>> FULL_KINETIC and CG might lead to slower convergence than FULL_ALL + DIIS, 
>> but my question lies in why convergence is not appreciably speeding up 
>> rather than its absolute speed.
>>
>> -Nick
>>
>> &DFT
>>
>>                 BASIS_SET_FILE_NAME BASIS_MOLOPT
>>
>>                 BASIS_SET_FILE_NAME BASIS_MOLOPT_UCL
>>
>>                 BASIS_SET_FILE_NAME BASIS_ADMM
>>
>>                 BASIS_SET_FILE_NAME BASIS_ADMM_MOLOPT
>>
>>                 POTENTIAL_FILE_NAME GTH_POTENTIALS
>>
>>                 UKS T
>>
>>                 MULTIPLICITY 0
>>
>>                 CHARGE 4
>>
>>                 &SCF
>>
>>                         MAX_ITER_LUMO 400
>>
>>                         MAX_SCF 50
>>
>>                         EPS_SCF 1e-06
>>
>>                         SCF_GUESS RESTART
>>
>>                         &OT
>>
>>                                 ALGORITHM STRICT
>>
>>                                 MINIMIZER CG
>>
>>                                 LINESEARCH 2PNT
>>
>>                                 PRECONDITIONER FULL_KINETIC
>>
>>                                 ENERGY_GAP 0.01
>>
>>                                 ROTATION F
>>
>>                                 OCCUPATION_PRECONDITIONER F
>>
>>                         &END OT
>>
>>                         &OUTER_SCF
>>
>>                                 EPS_SCF 1e-06
>>
>>                                 MAX_SCF 20
>>
>>                         &END OUTER_SCF
>>
>>                 &END SCF
>>
>>                 &AUXILIARY_DENSITY_MATRIX_METHOD
>>
>>                         ADMM_PURIFICATION_METHOD None
>>
>>                         METHOD BASIS_PROJECTION
>>
>>                 &END AUXILIARY_DENSITY_MATRIX_METHOD
>>
>>                 &QS
>>
>>                         EPS_DEFAULT 1e-12
>>
>>                         EPS_PGF_ORB 1e-16
>>
>>                         EXTRAPOLATION PS
>>
>>                         METHOD GPW
>>
>>                 &END QS
>>
>>                 &MGRID
>>
>>                         NGRIDS 5
>>
>>                         CUTOFF 550.0
>>
>>                         REL_CUTOFF 50.0
>>
>>                 &END MGRID
>>
>>  &XC
>>
>>                         &XC_FUNCTIONAL NO_SHORTCUT
>>
>>                                 &PBE
>>
>>                                         SCALE_X 0.0
>>
>>                                         SCALE_C 1.0
>>
>>                                 &END PBE
>>
>>                                 &XWPBE
>>
>>                                         SCALE_X 0.063
>>
>>                                         SCALE_X0 0.877
>>
>>                                         OMEGA 0.07
>>
>>                                 &END XWPBE
>>
>>                                 &PBE_HOLE_T_C_LR
>>
>>                                         SCALE_X 0.123
>>
>>                                         CUTOFF_RADIUS 5.930000000000001
>>
>>                                 &END PBE_HOLE_T_C_LR
>>
>>                         &END XC_FUNCTIONAL
>>
>>                         &HF
>>
>>                                 FRACTION 1.0
>>
>>                                 &SCREENING
>>
>>                                         EPS_SCHWARZ 1e-07
>>
>>                                         EPS_SCHWARZ_FORCES 1e-06
>>
>>                                         SCREEN_P_FORCES T
>>
>>                                         SCREEN_ON_INITIAL_P T
>>
>>                                 &END SCREENING
>>
>>                                 &INTERACTION_POTENTIAL
>>
>>                                         POTENTIAL_TYPE MIX_CL_TRUNC
>>
>>                                         OMEGA 0.07
>>
>>                                         SCALE_COULOMB 0.06
>>
>>                                         SCALE_LONGRANGE 0.063
>>
>>                                         CUTOFF_RADIUS 5.930000000000001
>>
>>                                         T_C_G_DATA t_c_g.dat
>>
>>                                 &END INTERACTION_POTENTIAL
>>
>>                                 &LOAD_BALANCE
>>
>>                                         RANDOMIZE T
>>
>>                                 &END LOAD_BALANCE
>>
>>                                 &MEMORY
>>
>>                                         EPS_STORAGE_SCALING 0.1
>>
>>                                         MAX_MEMORY 2000
>>
>>                                 &END MEMORY
>>
>>                         &END HF
>>
>>                 &END XC
>>
>> &END DFT
>>
>

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