<html><head></head><body><div class="ydp6c2522fdyahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><div><div dir="ltr" data-setdir="false"><div><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Dear QE experts</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">I am trying to calculate the phonon of NiCrSi using QE 6.5.</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Either i get<font color="#cd232c" style="background-color: inherit;"> negative frequency </font>or it <font color="#9d1811" style="background-color: inherit;">does not converge</font></span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">I tried with different values of <b>convergence criteria, q mesh, alpha_mix</b> in ph.in and <b>k mesh</b> in scf.in</span></div><div><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">tr2_ph = 1.0d-14, or</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">tr2_ph = 1.0d-12, or</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">tr2_ph = 1.0d-16,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">nq1 = 4, nq2 = 4, nq3 = 4, or </span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">nq1 = 3, nq2 =3, nq3 = 3, or</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> nq1 = 2, nq2 = 2, nq3 =2,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">alpha_mix(1) = 0.7, or</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> alpha_mix(1) = 0.3,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br>K_POINTS</div><div dir="ltr" data-setdir="false">12 12 12 or</div><div>16 16 16 </div><div><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">What could be the possible reason of getting negative frequency if the structure is considered as stable ? Appreciate if someone point out the possible mistakes</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Best Wishes</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">---------------------------------------------------------</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">#phonon of NiCrSi structure</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">&inputph</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">prefix = 'NiCrSi',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">tr2_ph = 1.0d-14,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">ldisp = .true.,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">nq1 = 4, nq2 = 4, nq3 = 4,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">amass(1) = 51.99,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">amass(2) = 28.08,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">amass(3) = 58.69,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> alpha_mix(1) = 0.7,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">outdir = './OUT',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">fildyn = 'NiCrSi.dyn',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">/</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">&control</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> calculation = 'scf',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> restart_mode = 'from_scratch',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> prefix = 'NiCrSi',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> pseudo_dir = '/home/sohail/pseudo',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> outdir = './OUT',</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">/</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">&system</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">ibrav = 2, a = 5.4559000675, b = 5.4559000675, c = 5.4559000675,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">cosAB = 0.0, cosBC = 0.0, cosAC = 0.0,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> nat = 3, ntyp = 3,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> ecutwfc = 75,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> ecutrho = 300,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> nbnd = 25,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> occupations = 'smearing', smearing = 'gaussian', degauss = 0.001,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">/</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">&electrons</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> mixing_beta = 0.3,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"> conv_thr = 1.0d-9,</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">/</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">ATOMIC_SPECIES</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Cr 51.99 Cr.pbe-sp-van.UPF</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Si 28.08 Si.pbe-n-van.UPF</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Ni 58.69 Ni.pbe-nd-rrkjus.UPF</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">ATOMIC_POSITIONS {alat}</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Cr 0.00000000 0.00000000 0.00000000</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Si 0.50000000 0.50000000 0.50000000</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">Ni 0.25000000 0.25000000 0.25000000</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">K_POINTS AUTOMATIC</span><br style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;"><span style="font-family: Helvetica Neue, Helvetica, Arial, sans-serif;">12 12 12 0 0 0</span></div><br></div><div>--------------------------------------------------------------------- <br></div><div class="ydp6c2522fdsignature"><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:16px;"><p><strong><font color="#0000ff" size="4">Sohail Ahmad</font></strong></p><p><font color="#0000ff">Department of Physics</font></p><p><font color="#0000ff">Faculty of Science, P. O. Box - 9004</font></p><p><font color="#0000ff">King Khalid University</font></p><p><font color="#0000ff">Abha, Saudi Arabia</font><font color="#0000ff"><br></font></p><p>--------------------------------------------------------------------<br></p></div></div></div></div></body></html>