[QE-users] negative phonon frequencies for InAs in QE 6.5

[Paolo Giannozzi]

"Negative" actually means "imaginary". If "negative" frequencies appear in
the three zero-frequency acoustic phonons at Gamma, and if they are small
(no more than a few tens of cm-1), there is nothing to worry about:
http://www.quantum-espresso.org/resources/faq/phonons#7.2

Paolo

On Thu, Jan 16, 2020 at 8:57 PM Sheikh Ziauddin Ahmed <sza9wz at virginia.edu>
wrote:

> Hello
>
> I am trying to compute the phonon frequencies ofI nAs. I am getting
> negative frequencies near the gamma point. I also tried with epsil =.true.
> But that does not change it. Here is the SCF and PH input I am using.
>
> Please give me some suggestions on what I can do to fix this problem.
>
> SCF:
>  &control
>     calculation='scf'
>     restart_mode='from_scratch',
>     prefix='test_i',
>     pseudo_dir = '/InAs_phonon',
>     outdir='./temp'
>     tstress = .true. ,
>     tprnfor = .true. ,
>  /
>  &system
>     ibrav=2, celldm(1) =11.4485, nat=2, ntyp=2,
>     ecutwfc = 50, ecutrho = 250
>  /
>  &electrons
>     conv_thr    = 1.0e-9
>     mixing_beta = 0.7
>     mixing_mode = 'local-TF'
>  /
> ATOMIC_SPECIES
>  In 114.818 In.pz-dn-kjpaw_psl.0.2.2.UPF
>  As 74.92 As.pz-n-kjpaw_psl.0.2.UPF
> ATOMIC_POSITIONS {crystal}
>  In 0.0 0.0 0.0
>  As 0.25 0.25 0.25
> K_POINTS automatic
> 6 6 6 0 0 0
>
>
> PH:
>  &inputph
>     tr2_ph=1d-14
>     prefix='test_i',
>     ldisp=.true.
>     !epsil=.true.
>     nq1=3, nq2=3, nq3=3
>     amass(1)=114.818
>     amass(2)=74.92
>     outdir='/scratch/sza9wz/'
>     fildyn = 'test_i-3.dyn'
>  /
>
> Regards,
> Sheikh Ahmed
> University of Virginia
> --
> *Sheikh Ziauddin Ahmed *
> PhD Candidate
> Charles L. Brown Department of Electrical and Computer Engineering
> University of Virginia
> Email:sza9wz*@virginia.edu* <sza9wz at virginia.edu>
> LinkedIn: https://www.linkedin.com/in/sheikh-ziauddin-ahmed
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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