[QE-users] Negative frequencies for phonon dispersion in Bilayer MoS2

[Giuseppe Scala]

Dear Chiara,

I've applied acoustic sum rules with my matdyn.in files in this way:

#############

&input
asr = 'simple'
flfrc = 'MoS2_BI_Dipole.fc'
flfrq = 'MoS2_BI_Dipole.freq'
q_in_band_form = .true.
q_in_cryst_coord = .true.
/
5
0.00 0.00 0.00 100 #Gamma
0.500 0.000 0.000 50 #M
0.3333 0.333 0.000 50 #K
0.000 0.000 0.000 100 #Gamma
0.500 0.000 0.000 1 #M

###############
and attached there's my matdyn.x file, my scf output file (MoS2_BI.out) and
my ph.x output file(MoS2_BI_ph333.out). You can also find  a picture of the
phonon dispersion relations.
kind regards,
Giuseppe


Il giorno gio 3 ago 2023 alle ore 09:03 Cignarella Chiara via users <
users at lists.quantum-espresso.org> ha scritto:

> Dear Giuseppe,
>
> Can you include also the output files?
>
> Did you apply the acoustic sun rules with matdyn.x (or dynmat)?
>
> Best
>
> Chiara Cignarella
> PhD student
> THEOS, EPFL Lausanne
>
> > On 3 Aug 2023, at 00:26, Giuseppe Scala <g.scala2 at campus.unimib.it>
> wrote:
> >
> > 
> > I get negative frequencies at gamma points for Bilayer MoS2. I relaxed
> my structure and checked convergence with respect to energy cutoff. That's
> my input file for the scf calculation:
> >
> > ##############
> >
> > &CONTROL
> > calculation ='scf'
> > prefix = 'MoS2_BI'
> > pseudo_dir = '/home/Giuseppe'
> > outdir = './'
> > tstress = .true.
> > tprnfor = .true.
> > forc_conv_thr = 1.0d-3
> > nstep = 200
> > /
> >
> >      &SYSTEM
> > ibrav = 4
> > a = 3.1429635960300000000
> > c = 20.006663000000000000
> > nat = 6
> > ntyp = 2
> > ecutwfc = 60
> > ecutrho = 240
> > occupations = 'smearing'
> > degauss = 0.01
> > /
> >
> >     &ELECTRONS
> > mixing_beta = 0.7
> > conv_thr = 1.0d-8
> > diagonalization = 'david'
> > electron_maxstep=200
> > /
> >
> >     &IONS
> > trust_radius_max = 0.2
> > /
> >     &CELL
> > cell_dynamics = "bfgs"
> > cell_dofree = '2Dxy'
> > /
> >
> > ATOMIC_SPECIES
> > Mo 95.9400 Mo.pbesol-spn-kjpaw_psl.1.0.0.UPF
> > S 32.0660 S.pbesol-n-kjpaw_psl.1.0.0.UPF
> > ATOMIC_POSITIONS {angstrom}
> > Mo 1.5714815237 0.9072955423 6.6890512735
> > Mo 0.0000000000 1.8145901001 13.377562735
> >  S 1.5714815237 0.9072955423 11.825385701
> >  S 1.5714815237 0.9072955423 14.928508325
> >  S 0.0000000000 1.8145901001 8.2412092563
> >  S 0.0000000000 1.8145901001 5.1381015776
> >
> > K_POINTS {automatic}
> > 4 4 4 0 0 0
> >
> > #########
> >
> >
> > And here my input file for ph.x
> >
> >
> > #######
> >
> > &inputph
> > prefix = 'MoS2_BI'
> > fildvscf = 'dvscf'
> > ldisp = .true.
> > fildyn = 'MoS2_BI.dyn'
> > alpha_mix(1) = 0.3
> > nq1 = 2,
> > nq2 = 2,
> > nq3 = 2,
> > tr2_ph = 1.0d-12
> > /
> > ########
> >
> > Is my bilayer wrong? I've come the exact same calculations for Bulk and
> Monolayer MoS2 and everything went smoothly
> >
> > _______________________________________________
> > The Quantum ESPRESSO community stands by the Ukrainian
> > people and expresses its concerns about the devastating
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> > and economic cooperation amongst peoples
> > _______________________________________________
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> > users mailing list users at lists.quantum-espresso.org
> > https://lists.quantum-espresso.org/mailman/listinfo/users
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
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