[QE-users] using Hybrid functional in QE

[Giuseppe Mattioli]

Dear Simon
The lack of pseudopotentials generated using a hybrid functional does  
not represent a significant source of error when using such  
functionals in calculations. I've run tons of B3LYP calculations using  
BLYP pseudopotentals and of PBE0 or HSE calculations using PBE  
pseudopotentials. PBE PPs are easier to find, while BLYP ones may be  
more difficult and sometimes you must (re)generate them yourself.

The input should be something like this (but check all the options in  
the pw input guide as they may be suitable/not suitable for your  
calculations):

  &control
     calculation = 'relax'
     restart_mode='from_scratch',
     prefix='$FILE',
     pseudo_dir = '$PSEUDO_DIR/',
     outdir='$TMP_DIR/',
     nstep=200,
  /
  &system
     ibrav=1, celldm(1)=40.0000,
     nat=87 ntyp=4,
     ecutwfc=90.0,
     ecutfock=130.0,
     occupations='smearing', degauss=0.01,
     nspin=1,
     input_dft='b3lyp'
     vdw_corr='grimme-d3',
  /
  &electrons
     diagonalization='david',
     mixing_mode='plain',
     mixing_beta=0.1,
     conv_thr=1.0d-6,
     electron_maxstep=100
     adaptive_thr=.true.
  /
  &ions
     ion_dynamics='bfgs'
  /
ATOMIC_SPECIES
O    15.999     O.blyp-mt.UPF
N    14.007     N.blyp-mt.UPF
C    12.011     C.blyp-mt.UPF
H     1.008     H.blyp-vbc.UPF
ATOMIC_POSITIONS {angstrom}
...
K_POINTS {gamma}

NB: I always recommend the use of norm-conserving pseudopotentials (in  
this case they are rather old but very well tested pseudopotentials  
that used to be in the QE repo, but you can generate BLYP PPs using  
the "atomic" ld1.x code and the PSlibrary, or even the ONCV generation  
code) when performing EXX calculations.
HTH
Giuseppe

Quoting Rameswar Bhattacharjee <rb1820 at georgetown.edu>:

> Hi Simon,
> Thank you for the information. I have gone through the input_dft and it
> looks like I can use PBE0 or B3LYP. But I am not sure for that case which
> pseudopotential I should use. Could you (or anyone) have a sample input to
> run a QUE calculation using the B3LYP functional? That would be very
> helpful. Thank you
>
> Rameswar
>
> On Fri, Jan 6, 2023 at 11:34 AM Simon Imanuel Rombauer <
> simon.rombauer at student.uni-augsburg.de> wrote:
>
>> Hello Rameswar,
>>
>> see 'input_dft' option in the documentation, see Modules/funct.f90 for
>> possible functionals.
>> Best,
>> Simon
>>
>> Am Freitag, Januar 06, 2023 17:00 CET, schrieb Rameswar Bhattacharjee <
>> rb1820 at georgetown.edu>:
>>
>> > Hi Everyone,
>> > I wonder if I can use hybrid functionals such as PBE0 or B3LYP in QE for
>> > ground state calculation. All the pseudopotentials I found on the website
>> > are for PBE. But I need an exchange-correlation functional (not pure) to
>> > calculate the band gap more accurately.
>> >
>> > Any suggestions would be appreciated. Thank you.
>> >
>> > Rameswar Bhattacharjee
>> > PostDoc
>> > Georgetown University
>>
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>