Dear Venkataramana Imandi,

Since you have fixed the lowest layers of the substrate, it sounds quasi impossible that only few layers would have moved that much (the interaction between the layers should be larger than the corrugation of the potential energy surface of the oxygen). Of course the coverage is quite high (1/2), but still I am surprised... Otherwise, I do not see anything "obviously wrong" in your input now.

    Greetings,

       apsi

-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
  Ari Paavo Seitsonen / ari.p.seitso...@iki.fi / http://www.iki.fi/~apsi/
    Ecole Normale Supérieure (ENS), Département de Chimie, Paris
    Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935


On Tue, 10 Apr 2018, Venkataramana Imandi wrote:

Dear Ari,

Sorry, I didn't mention that I also tried by fixing coordinate of O_ad at a 
bridge position.
It resulted the Pt atoms moving, in such way that O_ad becomes three-fold 
site(either fcc or hcp).

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


On Tue, Apr 10, 2018 at 2:44 PM, Venkataramana Imandi 
<venkataramana.ima...@gmail.com> wrote:

      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.

                                                                                
                     
??       ?                             






--
venkataramana

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