[Pw_forum] Problem with normal modes of NO gas phase

[Francesco Moriggi]

Hello, i'm Francesco Moriggi, a master student at the Milan University, i have a problem with ph.x. I am calculating NO frequency and i'm not reaching a convergence in values compared to cutoff energy, using norm conserving and ultrasoft pseudopotentials. Values i get are (i've put an image too in the email):

Cutoff   freq Norm    freq US

75        1879.0        1844.4

80        1875.5        1858.2

85        1890.6        1907.1

90        1923.5        1895.2

100      1889.6        1909.3

110      1914.2        1893.1

120      1890.5       1900.4

130       1890.7        1901.0

140        1914.7        1890.9

150        1886.9        ////

With Gaussian (aug-cc-pv5Z) i've got 1889.21 cm-1.

An example of the input of geometry optimization is:

&CONTROL
  calculation  = "relax",
  prefix       = "NO",
  pseudo_dir   = "/galileo/home/userexternal/fmoriggi/QE/NO/pseudoNO/ultrasoft",
  outdir       = "./out",
/
&SYSTEM
  ibrav     = 1,
  a         = 20,
  nat       = 2,
  ntyp      = 2,
  nspin     = 2,
  ecutwfc   = 150.D0,
  ecutrho = 1200.D0,
  occupations = 'smearing', smearing = 'gauss', degauss=0.02,
  starting_magnetization(1)=-0.9,
  starting_magnetization(2)=1.5,
/
&ELECTRONS
  electron_maxstep = 500,
  conv_thr    = 1.D-7,
  mixing_beta = 0.7D0,
/
&IONS
/
ATOMIC_SPECIES
O  16.00 O.pbe-van_ak.UPF
N  14.00 N.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
N  1.16 0.0  0.0
O  0.000  0.0  0.0  0 0 0
K_POINTS
1
0.0 0.0 0.0 1.0

Later i've done an scf  with a better conv_thr. This is the input.

&CONTROL
  calculation  = "scf",
  prefix       = "150",
  pseudo_dir   = "/galileo/home/userexternal/fmoriggi/QE/NO/pseudoNO/ultrasoft",
  outdir       = "./out150",
/
&SYSTEM
  ibrav     = 1,
  a         = 20,
  nat       = 2,
  ntyp      = 2,
  nspin     = 2,
  ecutwfc   = 150.D0,
  ecutrho   = 1200.D0,
  occupations = 'smearing', smearing = 'gauss', degauss=0.02,
  starting_magnetization(1)=-0.9,
  starting_magnetization(2)=1.5,
/
&ELECTRONS
  electron_maxstep = 500,
  conv_thr    = 1.D-9,
  mixing_beta = 0.7D0,
/
&IONS
/
ATOMIC_SPECIES
O  16.00 O.pbe-van_ak.UPF
N  14.00 N.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
N  1.166278 0.0  0.0
O  0.000  0.0  0.0  0 0 0
K_POINTS
1
0.0 0.0 0.0 1.0

And then i run the ph.x with this input:

phonon calculation - NO
 &inputph
  tr2_ph=4.0d-12,
  prefix='150'
  amass(1)=14.007,
  amass(2)=15.9994,
  outdir='/galileo/home/userexternal/fmoriggi/QE/NO/relax/ultra/out150'
 /
 0.0 0.0 0.0

If you can help me it would be very useful to my future TiO2 based calculations.


Best regards,

Francesco Moriggi

Webpage: http://users.unimi.it/ceotto/about_FrancescoMoriggi.html
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