Dear QE experts
I am trying to calculate the phonon of NiCrSi using QE 6.5.
Either i get negative frequency or it does not converge
I tried with different values of convergence criteria, q mesh, alpha_mix in
ph.in and k mesh in scf.in
tr2_ph = 1.0d-14, or
tr2_ph = 1.0d-12, or
tr2_ph = 1.0d-16,
nq1 = 4, nq2 = 4, nq3 = 4, or
nq1 = 3, nq2 =3, nq3 = 3, or
nq1 = 2, nq2 = 2, nq3 =2,
alpha_mix(1) = 0.7, or
alpha_mix(1) = 0.3,
K_POINTS12 12 12 or16 16 16
What could be the possible reason of getting negative frequency if the
structure is considered as stable ? Appreciate if someone point out the
possible mistakes
Best Wishes
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#phonon of NiCrSi structure
&inputph
prefix = 'NiCrSi',
tr2_ph = 1.0d-14,
ldisp = .true.,
nq1 = 4, nq2 = 4, nq3 = 4,
amass(1) = 51.99,
amass(2) = 28.08,
amass(3) = 58.69,
alpha_mix(1) = 0.7,
outdir = './OUT',
fildyn = 'NiCrSi.dyn',
/
&control
calculation = 'scf',
restart_mode = 'from_scratch',
prefix = 'NiCrSi',
pseudo_dir = '/home/sohail/pseudo',
outdir = './OUT',
/
&system
ibrav = 2, a = 5.4559000675, b = 5.4559000675, c = 5.4559000675,
cosAB = 0.0, cosBC = 0.0, cosAC = 0.0,
nat = 3, ntyp = 3,
ecutwfc = 75,
ecutrho = 300,
nbnd = 25,
occupations = 'smearing', smearing = 'gaussian', degauss = 0.001,
/
&electrons
mixing_beta = 0.3,
conv_thr = 1.0d-9,
/
ATOMIC_SPECIES
Cr 51.99 Cr.pbe-sp-van.UPF
Si 28.08 Si.pbe-n-van.UPF
Ni 58.69 Ni.pbe-nd-rrkjus.UPF
ATOMIC_POSITIONS {alat}
Cr 0.00000000 0.00000000 0.00000000
Si 0.50000000 0.50000000 0.50000000
Ni 0.25000000 0.25000000 0.25000000
K_POINTS AUTOMATIC
12 12 12 0 0 0
---------------------------------------------------------------------
Sohail Ahmad
Department of Physics
Faculty of Science, P. O. Box - 9004
King Khalid University
Abha, Saudi Arabia
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