<div dir="ltr">Thanks. I am trying to calculate the phonon dispersion of a superlattice consisting of InAs and AlSb. However, I am ending up with negative phonon frequencies for the structure. I used the epsil flag. But that did not help. How I can eliminate the negative phonon modes? <br><div><br></div><div>For relaxation I am using the following input: </div><div>&control<br> calculation='vc-relax'<br> restart_mode='from_scratch',<br> prefix='AlInAsSb'<br> tstress = .true. ,<br> tprnfor = .true. ,<br> verbosity ='high'<br> etot_conv_thr=1.0D-12<br> forc_conv_thr=1.0D-7<br> /<br> &system<br> ibrav=0, nat=10, ntyp=4,<br> ecutwfc = 50, ecutrho = 500<br> /<br> &electrons<br> electron_maxstep=1000<br> conv_thr = 1.0e-9<br> mixing_beta = 0.7 <br> mixing_mode = 'local-TF'<br> /<br> /<br>&IONS<br>/<br>&CELL<br> cell_dofree = 'z'<br>/<br>ATOMIC_SPECIES<br> Sb 121.76 Sb.pz-n-rrkjus_psl.1.0.0.UPF<br> Al 26.98 Al.pz-n-rrkjus_psl.0.1.UPF<br> As 74.92 As.pz-n-rrkjus_psl.0.2.UPF<br> In 114.82 In.pz-dn-rrkjus_psl.0.2.2.UPF<br>ATOMIC_POSITIONS {angstrom}<br>Sb 0.00000000 0.00000000 0.00000000<br>Sb 0.00000000 3.04570000 3.07106916<br>Sb 0.00000000 0.00000000 6.14213831<br>Al 1.52285000 1.52285000 1.53553458<br>Al -1.52285000 1.52285000 4.60660373<br>Al 1.52285000 1.52285000 7.67767289<br>As 0.00000000 3.04570000 9.21320747<br>As 0.00000000 0.00000000 12.24743004<br>In -1.52285000 1.52285000 10.73031875<br>In 1.52285000 1.52285000 13.76454133<br>K_POINTS automatic<br>6 6 6 0 0 0 <br>CELL_PARAMETERS {angstrom}<br>3.0457000000 3.0457000000 0.0000000000 <br>-3.0457000000 3.0457000000 0.0000000000 <br>0.0000000000 0.0000000000 15.2816526121 <br><br><br>For SCF run: </div><div>&control<br> calculation='scf'<br> restart_mode='from_scratch',<br> tstress = .true. ,<br> tprnfor = .true. ,<br> /<br> &system<br> ibrav=0, nat=10, ntyp=4,<br> ecutwfc = 50, ecutrho = 500<br> /<br> &electrons<br> conv_thr = 1.0e-9<br> mixing_beta = 0.7<br> mixing_mode = 'local-TF'<br> /<br>ATOMIC_SPECIES<br> Sb 121.76 Sb.pz-n-rrkjus_psl.1.0.0.UPF<br> Al 26.98 Al.pz-n-rrkjus_psl.0.1.UPF<br> As 74.92 As.pz-n-rrkjus_psl.0.2.UPF<br> In 114.82 In.pz-dn-rrkjus_psl.0.2.2.UPF <br>ATOMIC_POSITIONS {angstrom}<br>Sb 0.000000000 0.000000000 0.280559797<br>Sb 0.000000000 3.045700000 3.229150822<br>Sb 0.000000000 0.000000000 6.101422626<br>Al 1.522850000 1.522850000 1.784998522<br>Al -1.522850000 1.522850000 4.668823707<br>Al 1.522850000 1.522850000 7.525405573<br>As 0.000000000 3.045700000 8.683670011<br>As 0.000000000 0.000000000 11.527025485<br>In -1.522850000 1.522850000 10.092147868<br>In 1.522850000 1.522850000 13.117431792<br>K_POINTS automatic<br>6 6 6 0 0 0<br>CELL_PARAMETERS {angstrom}<br> 3.045700000 3.045700000 0.000000000<br> -3.045700000 3.045700000 0.000000000<br> 0.000000000 0.000000000 14.843532218<br><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Jan 2, 2020 at 3:54 PM Paolo Giannozzi <<a href="mailto:p.giannozzi@gmail.com">p.giannozzi@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr">On Mon, Dec 30, 2019 at 11:08 PM Sheikh Ziauddin Ahmed <<a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz@virginia.edu</a>> wrote:</div><div dir="ltr"><br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">I am trying to calculate the phonon dispersion of AlSb. I am getting two different results depending on how I am introducing the atoms in the SCF calculation. Will the order of the atom change the symmetry of the zinc blende AlSb?</div></blockquote><div><br></div><div>no. See attached.</div><div><br></div><div>PG<br></div><div> <br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>In the first case the input deck is: </div><div>&system<br> ibrav=2, nat=2, ntyp=2,<br> ecutwfc = 50, ecutrho = 500,<br> occupations='smearing',<br> smearing='gauss',<br> degauss=0.05,<br> celldm(1)=11.5944146,<br> /<br> &electrons<br> conv_thr = 1.0e-12<br> mixing_beta = 0.7<br> mixing_mode = 'local-TF'<br> /<br>ATOMIC_SPECIES<br> Al 26.98 al_lda_v1.uspp.F.UPF<br> Sb 121.76 sb_lda_v1.4.uspp.F.UPF<br>ATOMIC_POSITIONS (alat)<br> Al 0.0 0.0 0.0<br> Sb 0.25 0.25 0.25<br>K_POINTS automatic<br>6 6 6 0 0 0<br></div><div><br clear="all"><div>In the second case the input deck is: </div><div> &system<br> ibrav=2, nat=2, ntyp=2,<br> ecutwfc = 50, ecutrho = 500,<br> !occupations='smearing',<br> !smearing='gauss',<br> !degauss=0.05,<br> celldm(1)=11.5944146,<br> /<br> &electrons<br> conv_thr = 1.0e-12<br> mixing_beta = 0.7<br> mixing_mode = 'local-TF'<br> /<br>ATOMIC_SPECIES<br> Sb 121.76 sb_lda_v1.4.uspp.F.UPF<br> Al 26.98 al_lda_v1.uspp.F.UPF<br>ATOMIC_POSITIONS (alat)<br> Sb 0.0 0.0 0.0<br> Al 0.25 0.25 0.25<br>K_POINTS automatic<br>6 6 6 0 0 0<br></div><div><br></div><div>Thanks in advance!</div>-- <br><div dir="ltr"><div dir="ltr"><div style="margin-bottom:0px;margin-left:0px;padding-bottom:5px"><div><div dir="ltr"><span><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><font color="#444444"><b>Sheikh Ziauddin Ahmed </b></font></div><div style="font-size:12.8px"><font color="#444444">PhD Candidate</font></div><div style="font-size:12.8px"><font color="#444444">Charles L. Brown Department of Electrical and Computer Engineering</font></div><div style="font-size:12.8px"><font color="#444444">University of Virginia</font></div><div style="font-size:12.8px"><font color="#444444">Email<font color="#888888">:</font><a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz<u>@virginia.edu</u></a></font></div><div><div style="font-size:12.8px"><font color="#444444">LinkedIn</font><font color="#000000">: </font><span style="color:rgb(136,136,136);font-size:12.8px"><a href="https://www.linkedin.com/in/sheikh-ziauddin-ahmed" target="_blank">https://www.linkedin.com/in/sheikh-ziauddin-ahmed</a></span></div></div></div></div></div></div></div></span></div><div style="font-size:12.8px"></div></div></div><div style="font-size:12.8px"></div></div></div></div></div>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div style="margin-bottom:0px;margin-left:0px;padding-bottom:5px"><div><div dir="ltr"><span><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:12.8px"><font color="#444444"><b>Sheikh Ziauddin Ahmed </b></font></div><div style="font-size:12.8px"><font color="#444444">PhD Candidate</font></div><div style="font-size:12.8px"><font color="#444444">Charles L. Brown Department of Electrical and Computer Engineering</font></div><div style="font-size:12.8px"><font color="#444444">University of Virginia</font></div><div style="font-size:12.8px"><font color="#444444">Email<font color="#888888">:</font><a href="mailto:sza9wz@virginia.edu" target="_blank">sza9wz<u>@virginia.edu</u></a></font></div><div><div style="font-size:12.8px"><font color="#444444">LinkedIn</font><font color="#000000">: </font><span style="color:rgb(136,136,136);font-size:12.8px"><a href="https://www.linkedin.com/in/sheikh-ziauddin-ahmed" target="_blank">https://www.linkedin.com/in/sheikh-ziauddin-ahmed</a></span></div></div></div></div></div></div></div></span></div><div style="font-size:12.8px"></div></div></div><div style="font-size:12.8px"></div></div></div>