Dear QE users,
I am trying to calculate MgB2 superconducting Tc with lambda.x. As I understand
it, the correct value will be the one that is converged with respect to sigma
value (within plateau). However, I get a strange results without getting any
plateau and therefore can't pick the correct value. Values of sigma are default
(from 0.005 to 0.1). The output of lamda.x is given below:
lambda omega_log T_c
0.69701 640.588 22.047
0.74121 644.652 25.642
0.72855 644.807 24.658
0.71480 644.406 23.568
0.70317 644.049 22.646
0.68885 644.102 21.531
0.67095 644.454 20.150
0.65095 645.095 18.622
0.63044 645.881 17.069
0.61045 646.888 15.579
I will really appreciate if QE users/experts can help me resolve this problem
or highlight the correct procedure of picking Tc value.
Both scf and phonon calculations are nicely converged so I don't think
convergence is a problem. Input for scf and phonon calculations are given below:
scf
&control
calculation='scf',
prefix='MgB2',
pseudo_dir = '~/pseudo/',
outdir='./save/',
tprnfor = .true.,
tstress = .true.,
etot_conv_thr = 1.0d-5
forc_conv_thr = 1.0d-4
/
&system
ibrav = 4,
celldm(1) = 5.8260252227888,
celldm(3) = 1.1420694129095,
nat= 3,
ntyp = 2,
ecutwfc = 100
smearing = 'mp'
occupations = 'smearing'
degauss = 0.02
la2F = .true.,
/
&electrons
diagonalization = 'david'
mixing_mode = 'plain'
mixing_beta = 0.7
conv_thr = 1.0d-12
/
ATOMIC_SPECIES
Mg 24.305 Mg.pz-n-vbc.UPF
B 10.811 B.pz-vbc.UPF
ATOMIC_POSITIONS crystal
Mg 0.000000000 0.000000000 0.000000000
B 0.333333333 0.666666667 0.500000000
B 0.666666667 0.333333333 0.500000000
K_POINTS AUTOMATIC
16 16 16 0 0 0
phonon
e-ph MgB2
&inputph
prefix = 'MgB2',
fildyn = 'MgB2.dyn',
amass(1) = 24.305,
amass(2) = 10.811,
outdir = './save/'
ldisp = .true.,
trans = .true.,
fildvscf = 'dvscf',
nq1=8, nq2=8, nq3=8,
tr2_ph = 1.0d-14
electron_phonon='interpolated',
el_ph_sigma=0.005,
el_ph_nsigma=10,
/
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