Dear Venkataramana Imandi,
Possibly the bridge site is a saddle point but the symmetry is not
perfect, so the symmetry constrain does not fix the atom from moving
toward a lower-energy site. I would try arranging the surface so that for
example the x axis is the reaction coordinate for diffusion from a
three-fold site to the other three-fold site, and then fixing the value of
that coordinate (well, I do not remember if the fixed coordinates in the
input are for relative or Cartesian coordinates, but you could try fixing
a Cartesian one). If the bridge would be, however, a in-principle fully
symmetric coordinate it does not get fixed because the symmetries are not
found.
Greetings from Rüschlikon (ZH),
apsi
-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-
Ari Paavo Seitsonen / [email protected] / 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 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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