[Pw_forum] el-ph in Nb

[Iyad AL-QASIR]

Dear PWSCF users,
I am interested in el-ph calculations in Nb. I am studying the effect of
k-mesh size, smearing width, and smearing type on the el-ph constant and
phonon linewidths.

I am comparing Gaussian (gauss) and Fermi-Dirac (fd) using smearing width
0.022Ry =0.30 eV. I  am also using 64 64 64 k-mesh for el-ph and 16 16 16
k-mesh for the scf calculations. The calculations are performed with QE-5.0.

However, in case of Fermi-Dirac smearing the phonon calculations (ph.x)
proceed smoothly, whereas in case of Gaussian smearing the the phonon
calculations stops from the beginning with an error message : too many
kpoints ==> Why it works in case of (fd) and not in case of (gauss)
smearing???????


below is my input file for the el-ph calculations:
&control
 calculation='scf',
 restart_mode='from_scratch',
 title='Nb',
 outdir='./',
 prefix='Nb',
 pseudo_dir='./',
 wf_collect=.true.,
/
&system
 ibrav=3,
 celldm(1)=6.1389,
 nat=1, ntyp=1,
 ecutwfc=60.0,
 ecutrho=480.0,
 occupations='smearing',
 degauss=0.022,
 smearing='gauss',
 la2F= .true.,
/
&electrons
 conv_thr=1.0d-8,
 mixing_mode='plain',
 mixing_beta=0.7,
 diagonalization='cg',
/
ATOMIC_SPECIES
Nb 92.906 Nb.pz-sp-van.UPF
ATOMIC_POSITIONS {alat}
Nb  0.00 0.00 0.00
K_POINTS {automatic}
64 64 64 0 0 0

Kindest Regards,
___________________________
IYAD I. AL-QASIR, PhD
Postdoc Research Associate

X-Ray and Neutron Scattering and Spectroscopy Group
Materials Science and Technology Division
Oak Ridge National Lab
Oak Ridge, TN
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