[Pw_forum] HSE Screening Parameter

[Ref Fymz]

Hey Paolo
<http://www.mail-archive.com/search?l=pw_forum@pwscf.org&q=from:%22Paolo+Giannozzi%22>
,

The reason I chose such a ridiculously high screening parameter was to see
the difference between my highest occupied and lowest unoccupied states. I
was finding that regardless of whether the screening parameter was 0.0 all
the way to 100, I'm getting the same band gap for silicon (0.61 eV).

Thanks,

Phil

On 5 November 2015 at 09:02, Ref Fymz <reffymz at gmail.com> wrote:

> Dear pw_forum,
>
>
> I am trying to use the HSE hybrid functional within quantum espresso, I
> have an 8 atom cubic silicon cell, and I have converged my k-point grid,
> q-point grid, and my wavefunction ecut. However, regardless of how much I
> change my screening parameter (from 0.0 bohr^-1 all the way to 100
> bohr^-1), the difference between my lowest unoccupied and highest occupied
> state remains about 0.61 eV, this points towards a problem. Can anybody
> point me in the right direction?
>
> Also, when I do an scf run, I'm not getting the pressures / forces printed
> in the file, despite asking for them, is this due to the density of my
> k-point and q-point grid?
>
> The only other thing I can think it could be from is the ecutvcut /
> x_gamma_extrapolation / exxdiv_treatment. Has anybody else used QE for
> silicon successfully?
>
> My input looks like this;
>
>  &control
>     prefix='silicon',
>     pseudo_dir = 'espresso/pseudo/',
>     outdir='./tmp'
>     tprnfor = .true.
>     tstress = .true.
>     restart_mode = 'from_scratch'
>
>  /
>  &system
>     ibrav = 1, celldm(1) =10.327, nat= 8, ntyp= 1,
>     ecutwfc = 120, input_dft = 'hse'
>     nqx1 = 8, nqx2 = 8, nqx3 = 8
>     nbnd = 32
>     screening_parameter = 100
>     occupations = 'fixed'
>  /
>  &electrons
>     diagonalization='cg'
>     conv_thr = 1.0e-9
>  /
> ATOMIC_SPECIES
>  Si 28.086 Si.pbe-mt_fhi.UPF
>
> ATOMIC_POSITIONS alat
>  Si 0.0   0.0  0.0
>  Si 0.5   0.5  0.0
>  Si 0.5   0.0  0.5
>  Si 0.0   0.5  0.5
>  Si 0.25 0.25 0.25
>  Si 0.75 0.75 0.25
>  Si 0.75 0.25 0.75
>  Si 0.25 0.75 0.75
>
> K_POINTS automatic
> 24 24 24 0 0 0
>
>
>
> Thanks,
>
>
> Phil
>
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