[QE-users] O_ad(O-adsorption) is not binding at bridge position on Pt-surface

[Venkataramana Imandi]

Dear QE community,

I am a new user of Quantum espresso simulation package. I installed 6.2.1
Quantum espresso in the Linux-X86_64-INTEL-MPI. I want to find out the
binding energy of O_ad at various sites(top,bridge,hcp and fcc) on
Pt-surface and Pt-Ni alloy surface. In the beginning, i have tried on
Pt-surface, and I got O_ad at top, hcp and fcc sites on Pt-surface,
however, i couldn't find O_ad at bridge position.
I have tried all possible ways of getting O_ad at the bridge
position(between Pt-Pt). None of them were given succussful results, and
the resulted O_ad comes to either fcc or hcp position. All possible ways:
using with and without spin-polarization, davidson diagonalization anc cg,
option (nosym = .TRUE. and .FALSE.), mixing mode(plain, local-TF and TF),
changing mixing-beta(0.2, 0.3 and 0.5), neutral, negative charge(-2) and
different simulation setup (present 24 atoms to 48 Pt atoms). The last
option, i used different pseudopotential(Pt.pw91-n-van.UPF and
O.pw91-van_ak.UPF), herein, i got error as follows (Error in
scalartorealdp  Too few elements found). Now i stopped trials.
I ask you can anyone do calculation in your simulation setup with the given
input file, tell me the where the problem is.

I really thanks to you in advance for any suggestions regarding this.
For information, i used VASP in the last year, therein, i obtained O_ad at
all sites on Pt-surface.

 &control
    calculation='relax'
    restart_mode='from_scratch',
    pseudo_dir = '/home2/oth/ch18ipf01/pseudopotential2/',
    prefix='pt'
    tprnfor = .true.,
    nstep = 200
 /
 &system
    ibrav=0,
    nat=25,
    ntyp=2,
    ! nspin = 2,
    ! starting_magnetization(1)=0.7,
    ecutwfc = 32.0,
    ecutrho = 320.0,
    occupations='smearing',
    smearing='methfessel-paxton',
    degauss=0.02
   ! tot_charge = -2,
    nosym = .TRUE.
 /
 &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     3.45091550          1.17466050         13.69732100  1 1 1
Pt    4.84778787          1.20016667         12.44963917  1 1 1
Pt    3.46185858          3.60066659         12.44963917  1 1 1
Pt    2.07592929          1.20016667         12.44963917  1 1 1
Pt    0.69000000          3.60066659         12.44963917  1 1 1
Pt    3.46185858          0.40000000         10.18642611  1 1 1
Pt    4.84778787          2.80049996         10.18642611  1 1 1
Pt    0.69000000          0.40000000         10.18642611  1 1 1
Pt    2.07592929          2.80049996         10.18642611  1 1 1
Pt    3.46185858          2.00033330          7.92321305  1 1 1
Pt    4.84778787          4.40083326          7.92321305  1 1 1
Pt    0.69000000          2.00033330          7.92321305  1 1 1
Pt    2.07592929          4.40083326          7.92321305  1 1 1
Pt    4.84778787          1.20016667          5.66000000  1 1 1
Pt    3.46185858          3.60066659          5.66000000  1 1 1
Pt    2.07592929          1.20016667          5.66000000  1 1 1
Pt    0.69000000          3.60066659          5.66000000  1 1 1
Pt    3.46185858          0.40000000          3.39678694  0 0 0
Pt    4.84778787          2.80049996          3.39678694  0 0 0
Pt    0.69000000          0.40000000          3.39678694  0 0 0
Pt    2.07592929          2.80049996          3.39678694  0 0 0
Pt    3.46185858          2.00033330          1.13357388  0 0 0
Pt    4.84778787          4.40083326          1.13357388  0 0 0
Pt    0.69000000          2.00033330          1.13357388  0 0 0
Pt    2.07592929          4.40083326          1.13357388  0 0 0

K_POINTS {automatic}
3 3 1 0 0 0
CELL_PARAMETERS {angstrom}
5.5437171600     0.0000000000     0.0000000000
0.0000000000     4.8009999000     0.0000000000
0.0000000000     0.0000000000    25.5792783300


With best regards
Venkataramana Imandi
Postdoctoral fellow
IIT Madras, India.
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