[Pw_forum] PBE0 convergence

[Gabriele Sclauzero]

Dear Jie Jiang,

    Are you sure that your atomic structure is correct? We cannot judge since you did not provide the atomic positions. You can check by yourself using xcrysden, for instance. Do the standard PBE calculations work well and give meaningful results? For PBE0, you can maybe try to reduce the mixing_beta, or use another mixing scheme. Finally, are you sure about your k-point sampling? Your cell has celldm(2)=b/a < 1, then b<a, so why do you use more k-points along the first direction? I would rather use 3 6 1, instead of 6 3 1.

Regards,


in the behalf of Mr. PWscf,

   GS


Il giorno 31/mag/2011, alle ore 15.10, Jie Jiang ha scritto:

> Dear PWscf,
> 
> I get a problem in PBE0 convergence. Below is part of the input file,
> 
> &CONTROL
>   calculation  = "scf",
> /
> &SYSTEM
>   ibrav     = 12,
>   celldm(1) = 15.73981,
>   celldm(2) = 0.62519,
>   celldm(3) = 4.39673,
>   celldm(4) = 0.62519,
>   nat       = 58,
>   ntyp      = 5,
>   ecutwfc   = 80.0,
>   input_dft = 'pbe0',
>   nqx1 = 2, nqx2 = 1, nqx3 = 1,
>   exxdiv_treatment= 'gygi-baldereschi'
>   ecutvcut = 0.7
>   x_gamma_extrapolation= .TRUE.
>   occupations = "smearing",
>   smearing    = "methfessel-paxton",
>   degauss     = 0.01,
> /
> &ELECTRONS
>   conv_thr    = 1.D-6,
>   mixing_beta = 0.5D0,
> /
> ATOMIC_SPECIES
> C     12.0107    
> S     32.066     
> H     1.00794    
> O    15.9994     
> Zn   65.409     
> /
> K_POINTS {automatic}
>  6 3 1 0 0 0
> 
> The output 'dexx' is
> 
>      est. exchange err (dexx)  =       0.00059720 Ry
>      est. exchange err (dexx)  =      -0.02431459 Ry
>      est. exchange err (dexx)  =      -0.02596414 Ry
>      est. exchange err (dexx)  =      -0.02720608 Ry
>      est. exchange err (dexx)  =      -0.02821286 Ry
>      est. exchange err (dexx)  =      -0.02946368 Ry
>      est. exchange err (dexx)  =      -0.03148666 Ry
>      est. exchange err (dexx)  =      -0.03481403 Ry
>      est. exchange err (dexx)  =      -0.03964928 Ry
>      est. exchange err (dexx)  =      -0.04531623 Ry
> 
> and Fock energy is
> 
> -177.9185854736362
> -177.9185854736362        -177.8610717829301        -177.8047524875259
> -177.8047524875259        -177.8356769333793        -177.8179722072562
> -177.8179722072562        -177.8457748551563        -177.8216492155755
> -177.8216492155755        -177.8490273372818        -177.8219932983469
> -177.8219932983469        -177.8500300290520        -177.8216410368603
> -177.8216410368603        -177.8505498629616        -177.8205313239625
> -177.8205313239625        -177.8511288881755        -177.8187531280260
> -177.8187531280260        -177.8519180436694        -177.8154548907789
> -177.8154548907789        -177.8530355735678        -177.8113176980133
> -177.8113176980133        -177.8542927054368        -177.8066352532881
> 
> Can you please help me in this issue.
> 
> Thanks,
> 
> Jie Jiang
> 
> Applied Physics
> Yale University 
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§ Gabriele Sclauzero, EPFL SB ITP CSEA
   PH H2 462, Station 3, CH-1015 Lausanne

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