[CP2K-user] Band Gap Error for substituted compounds

[AFRID MAZHAR SHIRSEKAR]

Dear Nick,
Sorry for the troublesome articulation of the message. Yes the points you 
made are correct
PFA,
regards,
Afrid.

On Tuesday, October 27, 2020 at 11:45:44 AM UTC-4 n... at berkeley.edu wrote:

> Just to be clear, as I'm having a little trouble following you're message: 
> the expected outcome is that Sr substitution will decrease the band gap; 
> you substituted 2 Sr atoms in place of Ba, and this increased the band gap; 
> when you do a static calculation (no relaxation) the band gap does 
> decrease, but when you enable relaxation then the band gap increases.
>
> Are all three of those points correct?
>
> The next thing I would ask, if that is correct, is to see the output file.
> On Tuesday, October 27, 2020 at 8:02:01 AM UTC-7 a... at g.clemson.edu 
> wrote:
>
>> Dear developers,
>> I have been trying to study the effect on band gap, when substitutions 
>> are implemented on BaTiO3 structure. My methodology is that i generate a 2 
>> x 2 x 2 supercell of BaTiO3 and substitute 2 Sr atoms in the Ba positions, 
>> and then i conduct cell optimization on the new structure, and then i used 
>> the converged coordinates file and the unit cell parameters  from the 
>> output to  evaluate the band gap.
>> The band gap for BaTiO3 is around 3.2  ev, i used 37%hfx to approximate 
>> the bandgap closer to experimental one for BaTiO3 structure, but when the 
>> substitutions are implemented the calculation overestimates the band gap by 
>> 1 ev (4.2ev) which was expected to decrease from the initial value.
>> i calculated the bandgap without performing the cellopt and just 
>> substituted the Sr atoms in the coord file, and the result was in 
>> accordance with my hypothesis, ie decrease in the band gap.
>> I even tried keeping the symmetry during the cellopt calculations, but 
>> still the result was same. The scf guess parameter is set to atomic
>> below i attaching the input files for my calculations
>> Thanking you in anticipation
>> Sincerely 
>> Afrid.
>>
>> &GLOBAL
>>
>>   PROJECT perovskite_bandgap
>>
>>   RUN_TYPE ENERGY 
>>
>>   PRINT_LEVEL MEDIUM
>>
>> &END GLOBAL
>>
>>
>> &FORCE_EVAL
>>
>>   METHOD Quickstep
>>
>>   &DFT
>>
>>     BASIS_SET_FILE_NAME  BASIS_file 
>>
>>     POTENTIAL_FILE_NAME  POTENTIALS_file
>>
>>     BASIS_SET_FILE_NAME  BASIS_ADMM_MOLOPT
>>
>>     BASIS_SET_FILE_NAME  BASIS_ADMM
>>
>>     WFN_RESTART_FILE_NAME afrid-test-1.restart
>>
>>
>>     &PRINT                
>>
>>        &MO_CUBES
>>
>>        WRITE_CUBE .FALSE. 
>>
>>        NHOMO 1            
>>
>>        NLUMO 1            
>>
>>        &END
>>
>>     &END
>>
>>     &QS
>>
>>      METHOD GPW
>>
>>      EXTRAPOLATION PS 
>>
>>      EXTRAPOLATION_ORDER 3
>>
>>      EPS_DEFAULT 1.0E-10              #E-6
>>
>>     &END QS
>>
>>     &POISSON
>>
>>       PERIODIC XYZ
>>
>>     &END POISSON
>>
>>     &SCF
>>
>>       SCF_GUESS ATOMIC
>>
>>       EPS_SCF 1.0E-6                  #E-7
>>
>>       MAX_SCF 30
>>
>>       !EPS_LUMO 1.00000000E-005
>>
>>       !CHOLESKY INVERSE
>>
>>       
>>
>>       &OT
>>
>>        PRECONDITIONER FULL_SINGLE_INVERSE        #FULL ALL
>>
>>        MINIMIZER DIIS              # minimiser cg
>>
>>        ALGORITHM IRAC             #no algorithm before
>>
>>        ENERGY_GAP 0.01
>>
>>       &END
>>
>>       &OUTER_SCF 
>>
>> MAX_SCF 20
>>
>> EPS_SCF 1e-06
>>
>>       &END OUTER_SCF 
>>
>>       &MIXING
>>
>>         METHOD BROYDEN_MIXING
>>
>>         ALPHA 0.2
>>
>>         BETA 1.5
>>
>>         NBROYDEN 8
>>
>>       &END MIXING
>>
>>     &END SCF
>>
>>     &MGRID 
>>
>> CUTOFF 940
>>
>> REL_CUTOFF 80
>>
>> NGRIDS 5
>>
>> PROGRESSION_FACTOR 3
>>
>>     &END MGRID
>>
>>     &XC
>>
>>       &XC_FUNCTIONAL PBE
>>
>>        &PBE                  
>>
>>            SCALE_X 0.630
>>
>>            SCALE_C 1.0
>>
>>        &END
>>
>>       &END XC_FUNCTIONAL
>>
>>       &VDW_POTENTIAL
>>
>>         POTENTIAL_TYPE pair_potential
>>
>>         &PAIR_POTENTIAL
>>
>>           TYPE DFTD3(BJ)
>>
>>           PARAMETER_FILE_NAME dftd3.dat
>>
>>           REFERENCE_FUNCTIONAL PBE
>>
>>         &END PAIR_POTENTIAL
>>
>>       &END VDW_POTENTIAL
>>
>>       &HF
>>
>>         FRACTION 0.370         
>>
>>         &SCREENING            
>>
>>           EPS_SCHWARZ 1.0E-7
>>
>>           !SCREEN_ON_INITIAL_P TRUE  
>>
>>         &END                        
>>
>>         &MEMORY
>>
>>           MAX_MEMORY 7500   
>>
>>         &END
>>
>>         &INTERACTION_POTENTIAL      
>>
>>           POTENTIAL_TYPE TRUNCATED  
>>
>>           CUTOFF_RADIUS 3         
>>
>>           T_C_G_DATA ./t_c_g.dat    
>>
>>         &END                        
>>
>>       &END
>>
>>     &END XC
>>
>>     &AUXILIARY_DENSITY_MATRIX_METHOD 
>>
>> ADMM_PURIFICATION_METHOD NONE
>>
>> METHOD BASIS_PROJECTION
>>
>> &END AUXILIARY_DENSITY_MATRIX_METHOD
>>
>>   &END DFT
>>
>>
>>   &SUBSYS
>>
>>     &CELL
>>
>>       
>>
>>       A 8.043 0.000 0.000
>>
>>       B 0.014 7.998 0.000
>>
>>       C 0.014 0.019 7.998
>>
>>      
>>
>>       ALPHA_BETA_GAMMA 89.867 89.900 89.900
>>
>>       
>>
>>       
>>
>>       MULTIPLE_UNIT_CELL 1 1 1
>>
>>     &END CELL
>>
>>     
>>
>>     &TOPOLOGY
>>
>>       COORD_FILE_FORMAT XYZ
>>
>>       COORD_FILE_NAME BaTi03-cellopt-pos-1-converged.xyz
>>
>>       MULTIPLE_UNIT_CELL 1 1 1
>>
>>       
>>
>>     &END TOPOLOGY
>>
>>     &KIND Ba
>>
>>       ELEMENT   Ba
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q10
>>
>>       POTENTIAL GTH-PBE-q10
>>
>>       BASIS_SET AUX_FIT cFIT10
>>
>>     &END KIND
>>
>>     &KIND Ti
>>
>>       ELEMENT   Ti
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q12
>>
>>       POTENTIAL GTH-PBE-q12
>>
>>       BASIS_SET AUX_FIT cFIT10
>>
>>     &END KIND
>>
>>     &KIND O
>>
>>       ELEMENT   O
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q6
>>
>>       POTENTIAL GTH-PBE-q6
>>
>>       BASIS_SET AUX_FIT FIT9
>>
>>     &END KIND
>>
>>     &KIND Sr 
>>
>>       ELEMENT   Sr
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q10
>>
>>       POTENTIAL GTH-PBE-q10
>>
>>       BASIS_SET AUX_FIT cFIT10
>>
>>     &END KIND
>>
>>     &KIND Pb
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q4
>>
>>       POTENTIAL GTH-PBE-q4
>>
>>       BASIS_SET AUX_FIT cFIT9
>>
>>     &END KIND
>>
>>     &KIND Ca
>>
>>       BASIS_SET DZVP-MOLOPT-SR-GTH-q10
>>
>>       POTENTIAL GTH-PBE-q10
>>
>>       BASIS_SET AUX_FIT cFIT10
>>
>>     &END KIND
>>
>>   &END SUBSYS
>>
>>
>> &END FORCE_EVAL
>>
>>
>>
>>
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