[CP2K-user] [CP2K:16252] Re: Improve extrapolation between relaxation steps?

[Matt Watkins]

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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