[QE-users] NEB calculation

[mehrdad zamzamian]

Hi all dear QE users
I want to calculate the vacancy migration in alpha-Fe. I defined 2by2by2
supercell and used NEB but i could not achieve any convergence or a proper
result. searching in archives did not help. at the end of this message is
my input and a part of the output. I tested various changes like k-point,
ds,  num_of_images, PP ... but nothing happened.  my first image gave the
result of ~300eV!!!! then i gave some error (although the calculation was
being run) the second image was ~180 then the third image i gave ~300. i
also saw the atoms in xcrysden, they collapsed during the calculation!!!Is
there any idea about this problem? i appreciate.
------------------------------------------------------
BEGIN
BEGIN_PATH_INPUT
&PATH
  restart_mode      = 'from_scratch'
  string_method     = 'neb',
  nstep_path        = 50,
  ds                = 1.D0,
  opt_scheme        = "broyden",
  num_of_images     = 12,
  CI_scheme         = "no-CI",
  path_thr          = 0.1,
/
END_PATH_INPUT
BEGIN_ENGINE_INPUT
&CONTROL
  prefix         = ""
  pseudo_dir     = "",
/
&SYSTEM
    a                         =  5.69623e+00
    degauss                   =  1.00000e-02
    ecutrho                   =  2.25000e+02
    ecutwfc                   =  2.50000e+01
    ibrav                     = 1
    nat                       = 15
    nspin                     = 2
    ntyp                      = 1
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  2.00000e-01
/
&ELECTRONS
  mixing_beta = 0.01
  conv_thr =  1.0d-8
  electron_maxstep=200
/
&IONS
/
ATOMIC_SPECIES
Fe     55.84500  Fe.pbe-nd-rrkjus.UPF
BEGIN_POSITIONS
FIRST_IMAGE
ATOMIC_POSITIONS (angstrom)
Fe      0.000000   0.000000   0.000000
Fe      1.424058   1.424058   1.424058
Fe      0.000000   0.000000   2.848116
Fe      1.424058   1.424058   4.272174
Fe      0.000000   2.848116   0.000000
Fe      1.424058   4.272174   1.424058
Fe      0.000000   2.848116   2.848116
Fe      1.424058   4.272174   4.272174
Fe      2.848116   0.000000   0.000000
Fe      4.272174   1.424058   1.424058
Fe      2.848116   0.000000   2.848116
Fe      4.272174   1.424058   4.272174
Fe      2.848116   2.848116   0.000000
Fe      4.272174   4.272174   1.424058
Fe      2.848116   2.848116   2.848116
LAST_IMAGE
ATOMIC_POSITIONS (angstrom)
Fe      0.000000   0.000000   0.000000
Fe      1.424058   1.424058   1.424058
Fe      0.000000   0.000000   2.848116
Fe      1.424058   1.424058   4.272174
Fe      0.000000   2.848116   0.000000
Fe      1.424058   4.272174   1.424058
Fe      0.000000   2.848116   2.848116
Fe      1.424058   4.272174   4.272174
Fe      2.848116   0.000000   0.000000
Fe      4.272174   1.424058   1.424058
Fe      2.848116   0.000000   2.848116
Fe      4.272174   1.424058   4.272174
Fe      2.848116   2.848116   0.000000
Fe      4.272174   4.272174   1.424058
Fe      4.272174   4.272174   4.272174
END_POSITIONS
K_POINTS (automatic)
 5 5 5 0 0 0
END_ENGINE_INPUT
END
---------------------------------------
Best regards
S.M.Zamzamian
e-mail: mehrdad.zamzamian at gmail.com
Iran, Tehran
Sharif University of Technology
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