Dear Pw_users, I am trying to do calculation phonon dispersion and EPC for 1D Aluminum chain. I got the results which are strange phonon branches appearing. In the case of 2 atom-cell, I got 4 phonon branches, two of them are Optical and Acoustical phonon branches and two others, which have zero and negative values, are unknown for me. In the case if I have 1 atom-cell, that strange branch also appears. Could any body explain for me what kind of frequencies here?
I was surfing this forum and FAQ and I found many discussion about negative frequencies, but I still cannot find the answers for me. Bac This is my relaxed unitcell For 1-atom cell input alat = 20.0000 (a.u.) CELL_PARAMETERS (alat) 0.999558675 0.000000000 0.000000000 0.000000000 0.999558675 0.000000000 0.000000000 0.000000000 0.224680571 ATOMIC_POSITIONS (angstrom) Al 0.000000000 0.000000000 0.000000000 For 2-atom cell CELL_PARAMETERS (alat) 1.000000000 0.000000000 0.000000000 0.000000000 1.000000000 0.000000000 0.000000000 0.000000000 0.453300000 ATOMIC_POSITIONS (angstrom) Al 0.000000000 0.000000000 2.399000000 Al 0.000000000 0.000000000 0.000000000 And INPUT for ph.x tr2_ph=1.0d-12, prefix='al_20', fildvscf='Al2v', amass(1)=26.98, outdir='/root/tmp/', fildyn='al2.dyn', elph=.true., trans=.true., ldisp=.true. nq1=1, nq2=1, nq3=10 ------------------------------ Phung Viet Bac Division of Mathematical and Physical Science, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, JAPAN -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20071212/dc68af2d/attachment.htm
