Dear experts, To calculate the phonon along a specific path of BZ (K-Gamma-L) for Si, I used qplot = .true. and q_in_band_form = .true. (taking 2 points in between). Surprisingly, I got the following frequencies at Gamma, q = ( 0.000000000 0.000000000 0.000000000 )
************************************************************************** freq ( 1) = 11.535533 [THz] = 384.783979 [cm-1] freq ( 2) = 11.535533 [THz] = 384.783979 [cm-1] freq ( 3) = 11.535533 [THz] = 384.783979 [cm-1] freq ( 4) = 18.554595 [THz] = 618.914662 [cm-1] freq ( 5) = 18.554595 [THz] = 618.914662 [cm-1] freq ( 6) = 18.554595 [THz] = 618.914662 [cm-1] ************************************************************************** On the other hand, If I calculate only at Gamma point, I get q = ( 0.000000000 0.000000000 0.000000000 ) ************************************************************************** freq ( 1) = -0.117104 [THz] = -3.906180 [cm-1] freq ( 2) = -0.117104 [THz] = -3.906180 [cm-1] freq ( 3) = -0.117104 [THz] = -3.906180 [cm-1] freq ( 4) = 15.035771 [THz] = 501.539319 [cm-1] freq ( 5) = 15.035771 [THz] = 501.539319 [cm-1] freq ( 6) = 15.035771 [THz] = 501.539319 [cm-1] ************************************************************************** Why am I getting the large frequencies at Gamma if I calculate along K-Gamma-L? Do I need to specify Gamma always in the first?Why? My input files for the scf and phonon for Si are as the following. &control calculation = 'scf' prefix = 'Si' restart_mode = 'from_scratch' wf_collect = .true. pseudo_dir = './' outdir = './' / &system ibrav = 2 celldm(1) = 10.261217 nat = 2 ntyp = 1 ecutwfc = 45.0 / &electrons diagonalization = 'david' mixing_beta = 0.3 conv_thr = 1.0d-10 / ATOMIC_SPECIES Si 28.0855 Si.pz-vbc.UPF ATOMIC_POSITIONS alat Si 0.00 0.00 0.00 Si 0.25 0.25 0.25 K_POINTS automatic 8 8 8 0 0 0 Si &inputph outdir = './', prefix = 'Si', fildyn = 'Si.dyn', fildvscf = 'dvscf', ldisp = .true., tr2_ph = 1.0d-14 qplot = .true. q_in_band_form = .true. / 3 -0.7500000 0.7500000 0.0000000 2 ! K 0.0000000 0.0000000 0.0000000 2 ! G -0.5000000 0.5000000 0.5000000 1 ! L Thank You, Hari Paudyal SUNY Binghamton
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