[Pw_forum] How to control the convergence of hybrid functional calculations

[Giuseppe Mattioli]

Dear Wei-Bing
I do not claim a real expertise about HF-DFT calculations, but it seems to me 
that you should use a more dense grid of q-points (the nqx values) when 
dealing with your metallic system. Of course your calculation will become 
quite heavier... Moreover, have you checked, at least at a GGA level, that 50 
Ry are enough for your Pd pseudo?
Yours

Giuseppe

On Monday 05 July 2010 12:01:31 Wei-Bing Zhang wrote:
> Dear all
>
>
> I am trying to optimize the lattice parameters of Pd with PBE0 and HSE
> using QE 4.2. As done in lda/gga, I try to get the total energies with
> different lattice parameters and then fit them using EOS. However, I
> found the calculations can converge quickly at some lattice parameters
> (6.2 6.4 6.6 7.2 7.4) but fail to converge at others(6.8 7.0 7.6). I
> have let the calculations run more than 3 days and the calculations
> still did not converge.  I know hybrid functional calculations are
> very expensive but 3 days should be long enough for a single point
> energy calculations.  I think there should be something wrong in my
> calculations.
>
> Does anyone have the similar experience with me?  The input files are
> attached below. If I have missed something or there is something wrong
> in it, please point out.
>
> Thanks very much. Any suggestion about hybrid functional calculations
> will be highly appreciated.
>
> Best
>
> Wei-Bing Zhang
> ------------------------------------------
>  &control
>
>     calculation='scf'
>
>     restart_mode='from_scratch',
>
>     tprnfor = .true.
>
>     prefix='pbe0.6.8',
>
>     pseudo_dir = '/afs/ipp/home/w/weibingz/code/espresso-4.2/pseudo/',
>
>     outdir='/p5/batch/weibingz/temp/'
>
>  /
>
>  &system
>
>     ibrav=2, celldm(1) =6.8, nat=  1, ntyp= 1,
>
>     degauss=0.02,
>
>     smearing='mp',
>
>     occupations='smearing',
>
>     input_dft='pbe0', nqx1 = 1, nqx2 = 1, nqx3 = 1,
>
>     x_gamma_extrapolation = .TRUE.
>
>     ecutwfc = 50
>
>  /
>
>  &electrons
>
>     conv_thr =  1.0d-8
>
>     mixing_beta = 0.7
>
>  /
>
> ATOMIC_SPECIES
>
>  Pd 106.42   Pd.UPF
>
> ATOMIC_POSITIONS
>
>  Pd 0.00 0.00 0.00
>
> K_POINTS AUTOMATIC
>
> 14 14 14 1 1 1



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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
   v. Salaria Km 29,300 - C.P. 10                
   I 00016 - Monterotondo Stazione (RM)          
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