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<div>Dear developers,</div>
<div>Recently I was trying phonon calculations with spin, and was getting strange results, so I went down to one carbon atom in vacuum expecting frequencies to be close to zero. However, it seems that results vary a lot giving frequency -51 cm^-1 for C.pz-n-kjpaw_psl.0.1.UPF
pseudopotential, and ~900-1000 cm^-1 with C.pbe-van_bm.UPF pseudopotential. Otherwise the calculation seems to be running fine, so there is no way of knowing if there is a problem or not. I am using version 6.0 and including my inputs and excerpts from output.
Kindly please help me resolve this if you have any insights. Thank you!</div>
<div><br>
</div>
<div>Qiyuan Ruan</div>
<div><br>
</div>
<div><br>
</div>
<div>SCF input:</div>
<div>scf.in</div>
<div>&control</div>
<div> calculation='scf'</div>
<div> etot_conv_thr = 1.d-11,</div>
<div> verbosity='high',</div>
<div>/</div>
<div> &system</div>
<div> nat=1, ntyp=1,</div>
<div> ibrav=0,</div>
<div> ecutwfc=60.0, occupations='smearing', degauss = 0.01, smearing='mp',</div>
<div> la2F = .true.,</div>
<div> nspin = 2,</div>
<div> starting_magnetization(1) = 1,</div>
<div> nosym =.true.,</div>
<div> /</div>
<div> &electrons</div>
<div> mixing_beta = 0.5,</div>
<div> mixing_mode = 'local-TF'</div>
<div> conv_thr = 1.0d-12,</div>
<div> /</div>
<div>ATOMIC_SPECIES</div>
<div> C 12.01 C.pz-n-kjpaw_psl.0.1.UPF</div>
<div>CELL_PARAMETERS angstrom</div>
<div>10.000000000000000 0.000000000000000 0.000000000000000</div>
<div>0.000000000000000 10.000000000000000 0.000000000000000</div>
<div>0.000000000000000 0.000000000000000 10.000000000000000</div>
<div>ATOMIC_POSITIONS crystal</div>
<div>C 0.5 0.5 0.5</div>
<div>K_POINTS automatic</div>
<div>1 1 1 0 0 0</div>
<div><br>
</div>
<div>Phonon input:</div>
<div><br>
</div>
<div>&inputph</div>
<div> tr2_ph=1.0d-17,</div>
<div> alpha_mix(1)=0.3,</div>
<div> amass(1)=12.01,</div>
<div> niter_ph=500,</div>
<div> trans=.true.,</div>
<div> ldisp=.true.,</div>
<div> nq1=1, nq2=1, nq3=1,</div>
<div> start_q=1,</div>
<div> last_q=1,</div>
<div> /</div>
<div><br>
</div>
<div>Output for C.pz-n-kjpaw_psl.0.1.UPF:</div>
<div><br>
</div>
<div>Diagonalizing the dynamical matrix</div>
<div><br>
</div>
<div> q = ( 0.000000000 0.000000000 0.000000000 )</div>
<div><br>
</div>
<div> **************************************************************************</div>
<div> freq ( 1) = -1.543361 [THz] = -51.480967 [cm-1]</div>
<div> freq ( 2) = -1.540965 [THz] = -51.401048 [cm-1]</div>
<div> freq ( 3) = -1.538275 [THz] = -51.311315 [cm-1]</div>
<div>***************************************************************************</div>
<div>Output for C.pbe-van_bm.UPF:</div>
<div><br>
</div>
<div>Diagonalizing the dynamical matrix</div>
<div><br>
</div>
<div> q = ( 0.000000000 0.000000000 0.000000000 )</div>
<div><br>
</div>
<div> **************************************************************************</div>
<div> freq ( 1) = 26.838049 [THz] = 895.220954 [cm-1]</div>
<div> freq ( 2) = 30.156019 [THz] = 1005.896529 [cm-1]</div>
<div> freq ( 3) = 30.677843 [THz] = 1023.302678 [cm-1]</div>
<div> **************************************************************************</div>
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