[Pw_forum] H2 can NOT be absopted on FeO(111) surface

[Jian XU]

​​Dear all,

I'm sorry to interrupt you.

I'm new to QE. Recently, I'd like to do DFT calculation regarding hydrogen
absorption on FeO(111) surface.

A small slab model with 4 layers (two layers for O while the other two for
Fe and 1 atom in 1 layer) is established with O terminated. Hydrogen
molecule is placed about 2 A above O top site with parallel direction. The
input file is shown below.

However, the hydrogen molecule is move away from the surface during the
relax calcuation. Could you give me some suggestion on my work?

PS1: A some large slab model (4 atoms in 1 layer) is also established and
used for calculation, but the results are the same.
PS2: The non-polarized calculation make great influence on the absorption
of H2 on the surface? If the spin-polarized DFT is required for the
calculation, is there any suggestion on the input file?

Also I 'm confused by a problem.
The initial atoms position of the slab surface model (Structure A), is
relax to Structure B.
If the 'relax' calculation is implemented for slab surface and absorption
atoms (hydrogen molecule in my case), the atom position of slab surface in
the input file should be Structure A or B? Is there any difference between
the two choices?

Thanks for your time and patience in advance.


-------------------------------------------
cat > feo111.relax.in << EOF
&CONTROL
  calculation  = "relax",
  prefix       = "feo111",
  pseudo_dir   = "$PSEUDO_DIR",
  outdir       = "$TMP_DIR",
/

&SYSTEM
  ibrav     = 14,
  celldm(1) = 5.79,
  celldm(2) = 1.0,
  celldm(3) = 4.5,
  celldm(4) = 0.0,
  celldm(5) = 0.0,
  celldm(6) = -0.5,
  nat       = 6,
  ntyp      = 3,
  ecutwfc   = 25.0,
  occupations = 'smearing',
  smearing  = 'marzari-vanderbilt',
  degauss  = 0.01

/
&ELECTRONS
  conv_thr    = 1.D-7,
  mixing_beta = 0.7,

/
&IONS
/

ATOMIC_SPECIES
 Fe 55.845 Fe.pbe-nd-rrkjus.UPF
 O 15.999 O.pbe-rrkjus.UPF
 H 1.00794 H.pbe-rrkjus.UPF

ATOMIC_POSITIONS {crystal}

O        0.666654   0.333327   0.272813
O        0.333321   0.666660   0.090938
Fe       0.666654   0.333327   0.000000
Fe       0.999987   0.999994   0.181875
H        0.789366   0.333327   0.422813
H        0.543942   0.333327   0.422813


K_POINTS {automatic}
4 4 1 0 0 0





*————*

​
Jian XU

​
 ​
College of Materials Science and Engineering
Faculty of Engineering, Chongqing University
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