"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 <[email protected]> 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* <[email protected]> > LinkedIn: https://www.linkedin.com/in/sheikh-ziauddin-ahmed > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users -- 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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