[QE-users] Why does the difference between VASP and QE, even though they are BOMD theory

[Dr. Thomas Brumme]

Dear Venkataramana,

apart from the tips Pietro gave it is clear to me that you get differences
between QE and VASP. You're not using the same XC functional. PW91 and PBE
are not the same and as far as I remember they differ more for stuff like
surfaces or "reaction" barriers... Just search for papers which compare
these 2 functionals.

Regards

Thomas

Zitat von Venkataramana Imandi <venkataramana.imandi at gmail.com>:

> Dear QE users,
>
> Simulation cell parameters are same in the VASP and QE. In both cases,
> simulation started from the same input structure.
> I am using 6.2.1 version of QE.
> QE: I used the BFGS for geometry optimization, Davidson diagonalization for
> electronic scf and Pt(Pt.pbe-nd-rrkjus.UPF), O(O.pbe-rrkjus.UPF).
>
> VASP: I used RMM-DIIS for geometry optimization, Davidson diagaonalization
> or cg for electronic scf and Pt(PW91-ultrasoft), O(PW91-ultrasoft).
>
> For information,
>  I obtained all O_ad(O-adsorption) sites(top,bridge,hcp and fcc) on
> pt-surface in the VASP. In VASP, I found interlayer spacing(3rd and 2nd
> layer difference) varied +0.02 to +0.03 angstroms compared to initial
> structure.
>
> But in QE, I obtained all O_ad sites except bridge site on Pt-surface.
> In QE, I found interlayer spacing(3rd and 2nd layer difference) varied
>> +0.05 angstroms more compared to initital structure.
>
> Thus, I found more relaxed structure in QE compared to VASP.
>
> Any suggestions are greatly appreciated.
>
> My input file as follow.
>
>  &control
>     calculation='relax'
>     restart_mode='from_scratch',
>     pseudo_dir = '/home2/oth/ch18ipf01/pseudopotential2/',
>     prefix='pto'
>     tprnfor = .true.,
>     nstep = 200
>  /
>  &system
>     ibrav=0,
>     nat=49,
>     ntyp=2,
>     ! nspin = 2,
>     ! starting_magnetization(1)=0.7,
>     ecutwfc = 32.0,
>     ecutrho = 320.0,
>     occupations='smearing',
>     smearing='methfessel-paxton',
>     degauss=0.02
>  /
>  &electrons
>     diagonalization='cg'
>     conv_thr = 1.0e-6
>     mixing_beta = 0.3
>    electron_maxstep = 1000
>  /
> &ions
> ion_dynamics='bfgs',
>  /
> ATOMIC_SPECIES
> Pt  195.084  Pt.pbe-nd-rrkjus.UPF
> O    15.999  O.pbe-rrkjus.UPF
>
> ATOMIC_POSITIONS {angstrom}
> O   4.83670         3.24076         9.895064   1 1 1
> Pt  7.7079          5.67952         7.91015    1 1 1
> Pt  6.36297         8.19933         7.98784    1 1 1
> Pt  4.91919         6.00109         8.19464    1 1 1
> Pt  3.48056         8.20502         7.98339    1 1 1
> Pt  2.13171         5.68297         7.90776    1 1 1
> Pt  0.69985         8.11366         7.9477     1 1 1
> Pt  7.78611         0.73129         7.94675    1 1 1
> Pt  6.42371         3.08952         8.08857    1 1 1
> Pt  4.92315         0.76409         7.92858    1 1 1
> Pt  3.41889         3.09455         8.08213    1 1 1
> Pt  2.05589         0.73846         7.94323    1 1 1
> Pt  0.69979         3.32663         7.96547    1 1 1
> Pt  6.29321         4.95311         5.73597    1 1 1
> Pt  7.73513         7.49799         5.63702    1 1 1
> Pt  3.54425         4.96152         5.72897    1 1 1
> Pt  4.92162         7.32106         5.7753     1 1 1
> Pt  0.69791         5.10582         5.63088    1 1 1
> Pt  2.10707         7.50605         5.63432    1 1 1
> Pt  6.32478         0.10848         5.63611    1 1 1
> Pt  7.70985         2.61906         5.72581    1 1 1
> Pt  3.51897         0.11648         5.63414    1 1 1
> Pt  4.92144         2.53817         5.67277    1 1 1
> Pt  0.69984         0.23217         5.59048    1 1 1
> Pt  2.13138         2.62752         5.72184    1 1 1
> Pt  6.32344         6.78474         3.44718    1 1 1
> Pt  7.7339          9.3212          3.38713    1 1 1
> Pt  3.51851         6.7929          3.44491    1 1 1
> Pt  4.9219          9.19308         3.42498    1 1 1
> Pt  0.6991          6.90045         3.3778     1 1 1
> Pt  2.10972         9.32712         3.38533    1 1 1
> Pt  6.33835         1.94543         3.42008    1 1 1
> Pt  7.72421         4.42937         3.42142    1 1 1
> Pt  3.50426         1.95276         3.41781    1 1 1
> Pt  4.92063         4.34401         3.43929    1 1 1
> Pt  0.6992          2.09004         3.40181    1 1 1
> Pt  2.11503         4.43554         3.41785    1 1 1
> Pt  7.73571         6.2569          1.1        0 0 0
> Pt  6.32857         8.69414         1.1        0 0 0
> Pt  4.92143         6.2569          1.1        0 0 0
> Pt  3.51428         8.69414         1.1        0 0 0
> Pt  2.10714         6.2569          1.1        0 0 0
> Pt  0.7             8.69414         1.1        0 0 0
> Pt  7.73571         1.38241         1.1        0 0 0
> Pt  6.32857         3.81966         1.1        0 0 0
> Pt  4.92143         1.38241         1.1        0 0 0
> Pt  3.51428         3.81966         1.1        0 0 0
> Pt  2.10714         1.38241         1.1        0 0 0
> Pt  0.7             3.81966         1.1        0 0 0
>
> K_POINTS {automatic}
> 2 2 1 0 0 0
> CELL_PARAMETERS {angstrom}
> 8.4428549700000008    0.0000000000000000    0.0000000000000000
> 0.0000000000000000    9.7489691799999996    0.0000000000000000
> 0.0000000000000000    0.0000000000000000   19.1916000000000011
>
>
> With best regards
> Venkataramana Imandi
> Postdoctoral fellow
> IIT Madras, India.

-- 
Dr. rer. nat. Thomas Brumme
Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
Leipzig University
Phillipp-Rosenthal-Strasse 31
04103 Leipzig

Tel:  +49 (0)341 97 36456

email: thomas.brumme at uni-leipzig.de