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

[Sheikh Ziauddin Ahmed]

Thanks Paolo. When I introduced small smearing( about 0.02eV) the issue is
resolved. The smearing is significantly smaller than the bandgap. So is
introducing smearing for semiconductors correct?

On Fri, Jan 17, 2020 at 12:32 PM Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> "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
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
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-- 
*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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