[QE-users] Inconsistency | It seems that omega_ln is in the unit of meV rather than K

[Mitsuaki Kawamura]

Dear Dr. Jibiao Li

I performed the calculation by using your input files.
At the first q point [q = (0.0, 0.0, 0.0)], I obtained six imaginary
frequencies as follows:
     freq (    1) =     -64.626507 [THz] =   -2155.708217 [cm-1]
     freq (    2) =     -64.626507 [THz] =   -2155.708217 [cm-1]
     freq (    3) =     -64.626507 [THz] =   -2155.708217 [cm-1]
     freq (    4) =      -1.506110 [THz] =     -50.238408 [cm-1]
     freq (    5) =      -1.506110 [THz] =     -50.238408 [cm-1]
     freq (    6) =      -1.506110 [THz] =     -50.238408 [cm-1]
     freq (    7) =       1.768616 [THz] =      58.994680 [cm-1]
        :
Is it the same as your result?

I guess this structure is unstable.
It is better to relax the structure first.

Best regards,
Mitsuaki Kawamura

Institute for Solid State Physics, The University of Tokyo
Materials Design and Characterization Laboratory
Mitsuaki Kawamura
mkawamura at issp.u-tokyo.ac.jp

From: users <users-bounces at lists.quantum-espresso.org> On Behalf Of Jibiao
Li
Sent: Tuesday, May 4, 2021 4:24 PM
To: users <users at lists.quantum-espresso.org>
Subject: [QE-users] Inconsistency | It seems that omega_ln is in the unit of
meV rather than K

Dear All, 

I am trying to calculate Tc of the C-S-H system by simply replacing one S
atom by one C atom in the cubic cell. Followed by the instruction by Dr.
Mitsuaki Kawamura, I computed lambda and omega_ln with matdyn.x by using the
tetrahedron method (see the inputs).

However, I found the Tc would be too small if we take the unit of omega_ln
in Kelvin when comparing the outcome with that in references. On the
contrary, it would be more reasonable to treat it in the unit of meV. Is
omega_ln truly in Kelvin?  What's wrong with my calcualtions?

CHS: lambda=1.25, omega_ln=137.33 (K??)  Tc=Too small 
H3S: lambda=1.31, omega_log=127.93 meV, Tc=164 K  (Scientific Reports 7,
4473 (2017))
H3S: lambda=2.41, omega_log=109.00 meV, Tc=255 K  (Eur. Phys. J. B 89, 63
(2016))
H3S: lambda=2.58, omega_log=1336.0 K,     Tc=267 K  (Phys. Rev. B 91, 224513
(2015))


scf.inp(pw.x input)
 &CONTROL
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = './' ,
                  pseudo_dir = '/home/jibiaoli/pseudo/PAW' ,
                      prefix = 'bulk' ,
 /
 &SYSTEM
                       ibrav = 1,
                   celldm(1) = 5.365696156,
                         nat = 8,
                        ntyp = 3,
                     ecutwfc = 45 ,
                     ecutrho = 591 ,
                 occupations = 'tetrahedra_opt' ,
                    vdw_corr = 'grimme-d2' ,
 /
 &ELECTRONS
            electron_maxstep = 299,
                 mixing_beta = 0.2D0 ,
             diagonalization = 'david' ,
 /
ATOMIC_SPECIES
    C   12.01000  C.pbe-n-kjpaw_psl.1.0.0.UPF
    H    1.00794  H.pbe-kjpaw_psl.1.0.0.UPF
    S   32.06500  S.pbe-n-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS angstrom
H        1.419701496   1.419701496   0.000000000
H        0.000000000   1.419701496   0.000000000
H        1.419701496   0.000000000   0.000000000
H        0.000000000   1.419701496   1.419701496
H        0.000000000   0.000000000   1.419701496
H        1.419701496   0.000000000   1.419701496
C        1.419701496   1.419701496   1.419701496
S        0.000000000  -0.000000000   0.000000000
K_POINTS automatic
  12 12 12   0 0 0

ph.inp (ph.x input)
Phonon for CSH
&inputph
search_sym = .false.,
tr2_ph = 1.0d-14,
prefix = 'bulk',
fildvscf = 'aldv',
amass(1) = 12.0100,
amass(2) = 1.00794,
amass(3) = 32.0650,
outdir = './',
fildyn = 'bulk.dyn',
ldisp = .true.,
nq1 = 12, nq2 = 12, nq3 = 12,
/

elph.inp (ph.x input)
Electron-Phonon coefficients for CSH
&inputph
search_sym = .false.,
tr2_ph = 1.0d-14,
prefix = 'bulk',
fildvscf = 'aldv',
amass(1) = 12.0100,
amass(2) = 1.00794,
amass(3) = 32.0650,
outdir = './',
fildyn = 'bulk.dyn',
electron_phonon = 'lambda_tetra',
ldisp = .true.,
nq1 = 12, nq2 = 12, nq3 = 12,
nk1 = 24, nk2 = 24, nk3 = 24,
/
q2r.in
 &input
  zasr='simple',  fildyn='bulk.dyn', flfrc='bulk121212.fc', la2F=.true.
 /

matdyn.in.freq
 &input
    asr='simple',  amass(1) = 12.0100, amass(2) = 1.00794,amass(3) =
32.0650,
    flfrc='bulk121212.fc', flfrq='bulk1212112.freq', la2F=.true.,
dos=.false.
 /
  19
  0.000 0.0 0.0     0.0
  0.125 0.0 0.0     0.0
  0.250 0.0 0.0     0.0
  0.375 0.0 0.0     0.0
  0.500 0.0 0.0     0.0
  0.750 0.0 0.0     0.0
  1.000 0.0 0.0     0.0
  0.825 0.125 0.125 0.0
  0.750 0.250 0.250 0.0
  0.625 0.375 0.375 0.0
  0.500 0.500 0.500 0.0
  0.325 0.325 0.325 0.0
  0.250 0.250 0.250 0.0
  0.125 0.125 0.125 0.0
  0.000 0.000 0.000 0.0
  0.125 0.125 0.000 0.0
  0.250 0.250 0.000 0.0
  0.325 0.325 0.000 0.0
  0.500 0.500 0.000 0.0

matdyn.in.dos
 &input
    asr='simple',  amass(1) = 12.0100, amass(2) = 1.00794, amass(3) =
32.0650,
    flfrc='bulk121212.fc', flfrq='bulk121212.freq', la2F=.true., dos=.true.
    fldos='phonon.dos', nk1=12, nk2=12, nk3=12, ndos=100
 /