[CP2K-user] [CP2K:16141] Cell Optimization Not Converged for Copper

[GENG YUAN]

Hi Fabian,

Many thanks for your explanations!

Sincerely,
Geng

在2021年10月28日星期四 UTC-4 上午5:25:31<fabia... at gmail.com> 写道：

> Hi Geng,
>
> The plane wave basis depends on the size of the unit cell. Therefore, a 
> change of the cell dimensions corresponds to a change of basis. If the 
> energy difference that comes from this change of basis is large the 
> optimizer cannot converge. With CELL_REF you prevent this issue by fixing 
> the basis (which is now independent of the volume of the simulation domain).
>
> By the way, you are confusing the cell optimization and SCF: The SCF is 
> the energy minimization at each step of the cell optimization (and this 
> always converged). Only the cell optimization did not converge.
>
> Regarding the EPS_SCF: a tighter value can lower the number of cell 
> optimization steps, but each step will be more expensive. You have to test 
> it yourself.
>
> Cheers,
>
> Fabian
> On 27.10.2021 20:50, GENG YUAN wrote:
>
> Dear Fabian, 
>
> Many thanks for your reply. I added CELL_REF in my simulation and it works!
>
> Is it because that CELL_REF set a larger cell dimension, so the change of 
> my real cell volume during the cell_opt is always under this reference cell 
> volume, therefore the SCF could converge rather than keep fluctuating? 
> (please correct me if I'm wrong). I found some information saying that 
> CELL_REF is to fix the plane-wave basis whilst doing a cell_opt, but I 
> don't know what does this means (I will try searching more).
>
> About the EPS_SCF, do you have any suggestions about what criteria could I 
> apply instead of the one I used in my simulation (1.0E-06)?
>
> Many thanks for your help!
> Sincerely,
> Geng.
>
> 在2021年10月27日星期三 UTC-4 上午3:42:53<fabia... at gmail.com> 写道：
>
>> Hi Geng,
>>
>> Add a &CELL_REF section (
>> https://manual.cp2k.org/cp2k-8_2-branch/CP2K_INPUT/FORCE_EVAL/SUBSYS/CELL/CELL_REF.html). 
>> With 
>>
>> &CELL_REF
>>   ABC 10.83*1.5 10.83*1.5 7.22*1.5
>> &END
>>
>> the optimization converges within 35 steps. You could decrease EPS_SCF to 
>> reduce the noise in the forces.
>>
>> Cheers,
>>
>> Fabian
>> On 26.10.2021 23:02, GENG YUAN wrote:
>>
>> Dear CP2K Users, 
>>
>> I am attempting to run the cell optimization for a single bulk Cu (with 
>> 72 atoms). However, the SCF calculation can not converge: It reached the 
>> maximum number of optimization steps (500) and therefore exit the 
>> optimization. 
>>
>> I also tried changing the original lattice in my simulation (with 
>> associated coordinate) but it didn't work either.
>>
>> So far, the cell optimization only converged when I use a smaller bulk Cu 
>> (with 32 atoms). But we'd like to run a larger system.
>>
>> I've attached my input, output, the original Cu coordinate, as well as 
>> the trajectory during cell optimization here for your convenience. Any 
>> ideas are welcome! 
>>
>> Below is the input:
>> -----------------------------
>> &GLOBAL
>>   PROJECT Cu_cellopt
>>   RUN_TYPE CELL_OPT
>>   PRINT_LEVEL LOW
>> &END GLOBAL
>> &FORCE_EVAL
>>   METHOD QS
>>   STRESS_TENSOR ANALYTICAL
>>   &SUBSYS
>>     &CELL
>>       ABC 10.83 10.83 7.22
>>       SYMMETRY TETRAGONAL
>>     &END CELL
>>     &TOPOLOGY
>>      COORD_FILE_NAME ./Cu332.xyz
>>      COORDINATE xyz
>>     &END
>>     &KIND Cu
>>       BASIS_SET DZVP-MOLOPT-SR-GTH
>>       POTENTIAL GTH-PBE-q11
>>     &END KIND
>>   &END SUBSYS
>>   &DFT
>>     BASIS_SET_FILE_NAME ./BASIS_MOLOPT
>>     POTENTIAL_FILE_NAME ./GTH_POTENTIALS
>>     &QS
>>       EPS_DEFAULT 1.0E-12
>>     &END QS
>>     &MGRID
>>       CUTOFF 400
>>       NGRIDS 5
>>       REL_CUTOFF 60
>>     &END MGRID
>>     &SCF
>>       SCF_GUESS ATOMIC
>>       EPS_SCF 1.0E-06
>>       MAX_SCF 200
>>       ADDED_MOS 100
>>       &OUTER_SCF
>>         MAX_SCF 50
>>         EPS_SCF 1.0E-6
>>       &END
>>       &DIAGONALIZATION T
>>         ALGORITHM STANDARD
>>       &END DIAGONALIZATION
>>       &MIXING T
>>         METHOD BROYDEN_MIXING
>>         ALPHA 0.1
>>         NBROYDEN 8
>>       &END MIXING
>>       &SMEAR ON
>>         METHOD FERMI_DIRAC
>>         ELECTRONIC_TEMPERATURE [K] 500
>>       &END SMEAR
>>       &PRINT
>>         &RESTART ON
>>         &END RESTART
>>       &END PRINT
>>     &END SCF
>>     &XC
>>       &XC_FUNCTIONAL
>>          &LIBXC
>>            FUNCTIONAL XC_GGA_X_PBE_R
>>          &END
>>          &LIBXC
>>            FUNCTIONAL XC_GGA_C_PBE
>>          &END
>>       &END XC_FUNCTIONAL
>>       &VDW_POTENTIAL
>>          POTENTIAL_TYPE PAIR_POTENTIAL
>>          &PAIR_POTENTIAL
>>             LONG_RANGE_CORRECTION
>>             PARAMETER_FILE_NAME dftd3.dat
>>             TYPE DFTD3
>>             REFERENCE_FUNCTIONAL revPBE
>>          &END PAIR_POTENTIAL
>>        &END VDW_POTENTIAL
>>        &XC_GRID
>>         XC_DERIV NN50_SMOOTH
>>        &END XC_GRID
>>     &END XC
>>   &END DFT
>> &END FORCE_EVAL
>> &MOTION
>>   &CELL_OPT
>>     EXTERNAL_PRESSURE 0
>>     TYPE DIRECT_CELL_OPT
>>     KEEP_SYMMETRY TRUE
>>     MAX_DR    1.0E-05
>>     MAX_FORCE 1.0E-05
>>     RMS_DR    1.0E-05    
>>     RMS_FORCE 1.0E-05
>>     MAX_ITER 500
>>     OPTIMIZER BFGS
>>   &END CELL_OPT
>> &END MOTION 
>> ------------------------------------
>> Many thanks,
>> Geng.
>>
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