[QE-users] lambda.x and electron-phonon coupling in MgB2

[Mohammad Moaddeli]

Dear all,

I used lambda.x to calculate Tc for MgB2, as it explained in the
PHonon/.../example03.I have a question about the q-points and in the
lambda.in input file.
First time I used the sequence and weights of q-points calculated by
kpoints.x and I got Tc=9 K which is not correct.
Second time I used the sequence and weights of q-points calculated by ph.x
and I got 44 for Tc which is almost consistent with literature.
Can anyone help me find out which one is basically right?
I wonder why it is needed to reproduce q points by means of kpoints.x while
these q points are presented in ph.out and also elph_dir/elph.inp_lambda.*
files. Is it related to the algorithm of labmda.x, or the algorithm of
kpoints.x?

Thanks and Regards

==================================
Input file:
==================================
&CONTROL
    calculation='scf'
    restart_mode='from_scratch',
    outdir='tmp',
    prefix='mgb2',
    pseudo_dir = '/home/pseudo/',
    tstress =.TRUE.,
    tprnfor= .TRUE. ,
    verbosity='high' ,
/
&SYSTEM
    ibrav =4,
    celldm(1)= 5.824,
    celldm(3)=1.141,
    nat = 3,
    ntyp = 2,
    nspin = 1,
    ecutwfc = 120,
    occupations = 'smearing',
    degauss= 0.01,
    smearing= 'mp',
    la2f=.true.
/
&ELECTRONS
    conv_thr=1.D-11,
    mixing_beta=0.3,
/
ATOMIC_SPECIES
    Mg    24.305   Mg.pbe-hgh.UPF
    B     10.811   B.pbe-hgh.UPF

ATOMIC_POSITIONS (crystal)
   Mg       0.000000000   0.000000000   0.000000000
   B        0.333333333   0.666666666   0.500000000
   B        0.666666666   0.333333333   0.500000000

K_POINTS (Automatic)
   12 12 10  0 0 0
==========================================
electron-phonon coefficients for MgB2
&inputph
  tr2_ph=1.0d-14,
  prefix='mgb2',
  fildvscf='mgb2dv',
  amass(1)=24.305,
  amass(2)=10.811,
  outdir='tmp',
  fildyn='mgb2.dyn',
  electron_phonon='interpolated',
  el_ph_sigma=0.005,
  el_ph_nsigma=10,
  trans=.true.,
  ldisp=.true.
  nq1=6, nq2=6, nq3=5,
 /
===========================================

M Moaddeli, PhD
Pasargad HEI, Shiraz, Iran
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