[CP2K-user] EXTERNAL_PRESSURE and PRESSURE_TOLERANCE settings in cell optimisations for crystals

[Matt W]

You can find some good quality basis sets in in BASIS_MOLOPT_UCL:

https://github.com/cp2k/cp2k/blob/master/data/BASIS_MOLOPT_UCL

there are also some alternative Lanthanide basis sets available in other 
files.

Matt

On Wednesday, November 25, 2020 at 2:44:47 PM UTC sh... at gmail.com wrote:

> Dear Fabian,
> Thanks for the explanation! I've noticed the CELL_REF and OT issues of the 
> input file. The CP2K output file also hints about the OT algorithm.   
> The reason I use DZV-GTH-PADE basis for Y is that I cannot find GTH-PBE 
> basis set for it in the cp2k/data directory. Maybe I should find the 
> corresponding basis set in somewhere else.
> Anyway, thanks for your help and suggestions!
>
> Best regards.
> Huaiyang Sun
>
> On Wednesday, November 25, 2020 at 3:26:58 PM UTC+8 fa... at gmail.com 
> wrote:
>
>> Dear Huaiyang Sun,
>>
>> Many solids have a bulk modulus in the range of 1 to 100 GPa. A material 
>> with a bulk modulus of 10 GPa changes its volume by 1% when subjected to a 
>> pressure of 1000 bar. In this case a PRESSURE_TOLERANCE of 100 bar is 
>> already accurate to within 0.1% of the volume.
>>
>> The input file has some issues:
>> use CELL_REF for a cell optimization
>> you cannot use OT together with k-points, use DIAGONALIZATION instead
>> I would recomment to not mix different basis sets, especially not using 
>> PADE ones for PBE calculations
>>
>> Cheers,
>> Fabian
>> On Wednesday, 25 November 2020 at 04:09:02 UTC+1 sh... at gmail.com wrote:
>>
>>>
>>> Deal all,
>>>
>>> I'm doing a cell optimisation run of a YAG (Y3Al5O12) crystal. I wonder 
>>> about the meaning of the tags EXTERNAL_PRESSURE and PRESSURE_TOLERANCE in 
>>> the CELL_OPT section of the input. The default values are both 100 bar. 
>>> Here are the few points I don't understand,
>>>
>>> 1. If the cell optimisation run is targeted at the input 
>>> EXTERNAL_PRESSURE, shouldn't the default PRESSURE_TOLERANCE be given a much 
>>> smaller value, like 5.0 or 1.0 bar?
>>>
>>> 2. Why 100 bar? 1 atm = 1.013 bar sounds more reasonable.
>>>
>>> 3. My simple understanding of cell optimisation is to find the minimum 
>>> point of the energy-volume (E-V) curve. Then what's the role of external 
>>> pressure?
>>>
>>> Here is my input file.
>>>
>>> &GLOBAL
>>>   project  pristine-opt
>>>   run_type CELL_OPT
>>>   print_level MEDIUM
>>> &END GLOBAL
>>>
>>> &FORCE_EVAL
>>>   METHOD QS
>>>
>>>   &SUBSYS
>>>     &CELL 
>>>       ABC  12.0003 12.0003 12.0003  
>>>       PERIODIC XYZ 
>>>       MULTIPLE_UNIT_CELL  1   1   1
>>>       SYMMETRY CUBIC 
>>>     &END CELL
>>>
>>>     &TOPOLOGY
>>>       MULTIPLE_UNIT_CELL  1   1   1
>>>       COORD_FILE_FORMAT XYZ
>>>       COORD_FILE_NAME yag_from_cif_conven_unit.xyz 
>>>     &END TOPOLOGY
>>>
>>>     &KIND Y
>>>       ELEMENT Y
>>>       BASIS_SET DZV-GTH-PADE
>>>       POTENTIAL GTH-PBE-q11
>>>     &END KIND 
>>>
>>>
>>>     &KIND Al
>>>       ELEMENT Al
>>>       BASIS_SET DZVP-MOLOPT-SR-GTH 
>>>       POTENTIAL GTH-PBE-q3
>>>     &END KIND 
>>>
>>>     &KIND O
>>>       ELEMENT O
>>>       BASIS_SET DZVP-GTH-PBE
>>>       POTENTIAL GTH-PBE-q6
>>>     &END KIND
>>>
>>>     &KIND Ce
>>>       ELEMENT Ce
>>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q12
>>>       POTENTIAL GTH-PBE-q12
>>>     &END KIND
>>>
>>>     &KIND Yb
>>>       ELEMENT Yb
>>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q24
>>>       POTENTIAL GTH-PBE-q24
>>>     &END KIND
>>>
>>>   &END SUBSYS
>>>
>>>   &DFT
>>>     BASIS_SET_FILE_NAME BASIS_SET_YAG
>>>     POTENTIAL_FILE_NAME POTENTIAL_YAG
>>>
>>>     &MGRID
>>>       NGRIDS 4
>>>       CUTOFF 600
>>>       REL_CUTOFF 60
>>>     &END MGRID
>>>
>>>     &QS
>>>       EPS_DEFAULT 1.0E-12
>>>     &END QS
>>>
>>>     &POISSON
>>>       PERIODIC XYZ
>>>     &END POISSON
>>>
>>>     &SCF
>>>       SCF_GUESS ATOMIC
>>>       EPS_SCF 5.0E-7
>>>       MAX_SCF 200 
>>>
>>>       CHOLESKY INVERSE 
>>>
>>>       &OT ON
>>>         MINIMIZER DIIS
>>>       &END OT
>>>       #&DIAGONALIZATION 
>>>       #  ALGORITHM STANDARD
>>>       #&END DIAGONALIZATION 
>>>
>>>       # ADDED_MOS 30
>>>       #
>>>       # &SMEAR ON
>>>       # METHOD FERMI_DIRAC
>>>       # ELECTRONIC_TEMPERATURE [K] 300
>>>       #&END SMEAR 
>>>
>>>       # &MIXING
>>>       #  METHOD BROYDEN_MIXING
>>>       #  ALPHA 0.4
>>>       #  BETA 0.5
>>>       #  NBROYDEN 8
>>>       # &END MIXING 
>>>     &END SCF
>>>
>>>     &XC
>>>       &XC_FUNCTIONAL PBE
>>>       &END XC_FUNCTIONAL 
>>>     &END XC
>>>
>>>     &KPOINTS
>>>       EPS_GEO 1.0E-5
>>>       SCHEME MONKHORST 3 3 3
>>>     &END KPOINTS
>>>   &END DFT
>>>
>>>   &PRINT
>>>     &TOTAL_NUMBERS ON
>>>     &END TOTAL_NUMBERS
>>>   &END PRINT
>>>   
>>>   STRESS_TENSOR ANALYTICAL 
>>> &END FORCE_EVAL
>>>
>>> &MOTION
>>>   &GEO_OPT
>>>     OPTIMIZER LBFGS
>>>     TYPE MINIMIZATION
>>>     MAX_DR   5.0E-4
>>>     MAX_FORCE 5.0E-4
>>>     RMS_DR  5.0E-4
>>>     RMS_FORCE 5.0E-4
>>>     MAX_ITER 500
>>>   &END GEO_OPT
>>>
>>>   &CELL_OPT
>>>     TYPE DIRECT_CELL_OPT
>>>     OPTIMIZER LBFGS
>>>     KEEP_SYMMETRY
>>>     MAX_DR 5.0E-4
>>>     MAX_FORCE 1.0E-4
>>>     RMS_DR 5.0E-4
>>>     RMS_FORCE 5.0E-4
>>>     # defaults for p and delta p [bar]
>>>     EXTERNAL_PRESSURE   100.0 0.0 0.0    0.0 100.0 0.0   0.0 0.0 100.0
>>>     PRESSURE_TOLERANCE  100.0
>>>   &END CELL_OPT
>>> &END MOTION 
>>>
>>>
>>>
>>>
>>> Thank you,
>>> Huaiyang Sun
>>>
>>>
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