Dear Andrea, Have you tried using more q-points? Can you send me the picture to have a look at?
Bests, Eyvaz. ------------------------------------------------------------------- Prof. Eyvaz Isaev, Department of Physics, Chemistry, and Biology (IFM), Linkoping University, Sweden Theoretical Physics Department, Moscow State Institute of Steel & Alloys, Russia, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com ----- Original Message ---- From: Andrea Salguero <[email protected]> To: "pw_forum at pwscf.org" <pw_forum at pwscf.org> Sent: Sat, January 15, 2011 1:20:18 AM Subject: [Pw_forum] missing imaginary frequencies Dear Pwscf community: I have calculated the phonon frequencies of a metallic system along different high symmetry points in the BZ and also the phonon dispersion of it. I see two instabilities at z-point in the dispersion plot but I obtain no imaginary/negative frequencies when I calculate only for that point. I used the same parameters in the input files for both calculations and I followed the procedure from the examples directory of PWSCF(example02) for the calculation of the frequencies at Z point: 1) a scf calculation 2) then the calculation of the dynamical matrix at z-point (0,0,0.5), my input file: &inputph tr2_ph=1.0d-14, amass(1)=183.84d0, amass(2)=15.9994d0, prefix='case', outdir = '', fildyn='case.dynZ', / 0.0 0.0 0.5 what am I doing wrong or what am I missing? Any help would be appreciated, Best Regards Andrea ******************************************************** Andrea Salguero School of Applied and Engineering Physics Cornell University, Ithaca NY ******************************************************** _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
