[Pw_forum] problem hybrid pseudopotential calculations
Muhammad Adnan Saqlain
adnansaqlain at gmail.com
Sat Jul 23 16:21:59 CEST 2016
Dear Stefano
Thanks for your mail.
But what does this error mean? when I try to run the calculation, it ejects
this error? How can I get rid of it
Error in routine setup (1):
Variable cell and EXX not tested!
The input file is as under
&CONTROL
title = 'CsPbI' ,
calculation = 'vc-relax' ,
restart_mode = 'from_scratch' ,
outdir = '/work/saqlain' ,
wfcdir = '/work/saqlain' ,
pseudo_dir = '/home/ibm/proj/proj527/saqlain/psp' ,
prefix = 'PBE0' ,
/
&SYSTEM
ibrav = 0,
celldm(1) = 1.8897265,
nat = 5,
ntyp = 3,
ecutwfc = 40 ,
input_dft = 'PBE0' ,
occupations = 'smearing' ,
degauss = 0.001 ,
smearing = 'marzari-vanderbilt' ,
ecutfock = 40 ,
exxdiv_treatment = 'none' ,
nqx1 = 2 ,
nqx2 = 2 ,
nqx3 = 2 ,
/
&ELECTRONS
/
&IONS
/
&CELL
/
CELL_PARAMETERS cubic
6.382434987 0.000000000 0.000000000
0.000000000 6.382434987 0.000000000
0.000000000 0.000000000 6.382434987
ATOMIC_SPECIES
Cs 132.90000 Cs.pbe-sp-hgh.UPF
I 126.90000 I.pbe-hgh.UPF
Pb 207.20000 Pb.pbe-hgh.UPF
ATOMIC_POSITIONS crystal
Cs 0.500000000 0.500000000 0.500000000
I 0.500000000 0.000000000 0.000000000
I 0.000000000 0.500000000 0.000000000
I 0.000000000 0.000000000 0.500000000
Pb 0.000000000 0.000000000 0.000000000
K_POINTS automatic
2 2 2 1 1 1
On Sat, Jul 23, 2016 at 6:48 PM, stefano de gironcoli <degironc at sissa.it>
wrote:
> On 23/07/2016 14:23, Muhammad Adnan Saqlain wrote:
>
> Dear Stefano
> thanks for your response.
> Can you please guide me (1) Why vc-relax is not allowed in Q-E 5.4.0?
>
> it is.
>
> (2) How would the band gap be effected if I relax the cell without hybrid
> scheme and then calculate band gap with hybrid one?
>
> it would be the band gap of a different structure.
> it would depend on how different the structure would be with a different
> functional.
>
> stefano
>
>
> On Sat, Jul 23, 2016 at 1:07 PM, stefano de gironcoli <degironc at sissa.it>
> wrote:
>
>> dear Muhammad Adnan Saqlain,
>>
>> gamma extrapolation is a way to deal with the ill defined value of the
>> exchange integral between wfcs at k and k+q in the limit of q->0.
>> if you use a truncated coulomb interaction that limit is not ill
>> defined.
>> no need to use the gamma_extrapolation option
>> best,
>> stefano
>>
>> On 23/07/2016 10:00, Muhammad Adnan Saqlain wrote:
>>
>> Dear Prof Clavijo
>> I am extremely sorry for my misleading title of the calculation.
>> Actually, It was a cubic structure consisting of Cs, Pb and I. I
>> deliberately did not put the atoms in the calculation. more over I do not
>> know why the algorithm for cell movement was not copied it was however
>> present in the input file.
>>
>> 1. If I try these two options, the
>>
>> vcut_spherical : appropriate for cubic and quasi-cubic supercells
>> vcut_ws : appropriate for strongly anisotropic supercells, see also
>> ecutvcut.
>>
>> the program says like this
>>
>>
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>> Error in routine system_checkin (1):
>> x_gamma_extrapolation cannot be used with vcut
>>
>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>
>> I have no idea how to fix it. Can you suggest one??
>>
>> 2. I have now used Q-E 5.4.0, but this version does not allow vc-relax
>> option with hybrid one. why is it so? How would the band gap be effected if
>> I relax the cell without hybrid scheme and then calculate band gap with
>> hybrid one?
>>
>> 3. About the ecutoff, I deliberately used small one as these are just
>> calculations not the real one.
>> 4. I have cubic system, may I try q-grid like 1*2*3 or it has to be
>> symmetric one?
>> 5. Can you suggest more about hybrid calculations?
>>
>>
>> On Fri, Jul 22, 2016 at 10:09 PM, Josue Itsman Clavijo Penagos <
>> jiclavijop at unal.edu.co> wrote:
>>
>>> Dear, Muhammad Adnan Saqlain, remember the user documentation for
>>> *exxdiv_treatment*:
>>>
>>> Specific for EXX. It selects the kind of approach to be used
>>> for treating the Coulomb potential divergencies at small q vectors.
>>>
>>> gygi-baldereschi : appropriate for cubic and *quasi-cubic supercells*
>>> vcut_spherical : appropriate for cubic and quasi-cubic supercells
>>> vcut_ws : appropriate for strongly anisotropic supercells, see also
>>> ecutvcut.
>>> none : sets Coulomb potential at G,q=0 to 0.0 (required for GAU-PBE)
>>>
>>> *Besides that, *I have some observations and suggestions for you based
>>> in the input file you send, so you can realize why does QE is failing when
>>> trying to simulate your system:
>>>
>>> 1 - Check if you really need to apply smearing, since this technique is
>>> intended to be useful for metallic systems, and Anatase is cleary not a
>>> metallic system, in fact, is more a Wide-gap or Insulator -type system.
>>>
>>> 2 - You do want to perform a vc-relax calculation, but nothing are
>>> specified in the cards &IONS and &CELL. There is not cell relaxing
>>> algorithm specified (BFGS? MD?)
>>>
>>> 3 - The card &ATOMIC_POSITIONS shows nothing: No atoms, no cell to relax.
>>>
>>> 4 - In the card &SYSTEM , *ecutwfc = 40.* This, in my humble opinion, a
>>> very poor cutoff for a serious calculation. Do a ecutwfc convergence test
>>> before attempt your system.
>>>
>>> 5 - Please take in account that a hybrid calculation is VERY expensive
>>> in terms of computational demand, so if you set up a vc-relax calculation
>>> using hybrid PPS you must test if *nqx1 = 1, 2 or 3 really makes a
>>> difference.*
>>>
>>> *6 - For some systems, input_dft=HSE is faster than **input_dft =
>>> "PBE0". Check if that could be your case.*
>>>
>>> By the way, are you sure Anatase has a cubic crystal structure? Does
>>> XCrysden show the correct structure for your input?
>>>
>>> *Best regards, *
>>>
>>>
>>> Josué Clavijo, PhD.
>>> Assistant Professor
>>> Universidad Nacional de Colombia
>>> Departamento de Química
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://pwscf.org/mailman/listinfo/pw_forum
>>>
>>
>>
>>
>> --
>> Best Regards
>> Muhammad Adnan Saqlain
>>
>>
>>
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>
>
>
> --
> Best Regards
> Muhammad Adnan Saqlain
>
>
>
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--
Best Regards
Muhammad Adnan Saqlain
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