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Hi everyone,</div>
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I would like to use Quantum ESPRESSO to calculate the Raman intensity in rutile TiO2. The Raman-active modes I find agree very well with experiment, but ph.x also predicts a handful of negative-frequency modes which I cannot eliminate. I have tried increasing
ecutwfc and the density of k-points in the SCF calculation, to no effect. I have attached my input/output files below. The lattice parameters/atomic coordinates result from a vc-relax calculation with a 7x7x11 k-mesh. </div>
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If anyone could suggest a fix for this, I would greatly appreciate it.</div>
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Thank you for your time,</div>
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Connor Wilson</div>
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Condensed Matter and Materials Science</div>
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Brock University</div>
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St. Catharines , ON, CAN</div>
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! pw.x</div>
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&CONTROL
<div class="FluidPluginCopy ContentPasted0"> calculation='scf',</div>
<div class="FluidPluginCopy ContentPasted0"> restart_mode='from_scratch',</div>
<div class="FluidPluginCopy ContentPasted0"> prefix = 'TiO2',</div>
<div class="FluidPluginCopy ContentPasted0"> etot_conv_thr = 1.0d-6,</div>
<div class="FluidPluginCopy ContentPasted0"> forc_conv_thr = 1.0d-6,</div>
<div class="FluidPluginCopy ContentPasted0"> pseudo_dir = '/home/cw279/pseudo',</div>
<div class="FluidPluginCopy ContentPasted0"> outdir = '/home/cw279/projects/def-crandles/cw279/TiO2/ph',</div>
<div class="FluidPluginCopy ContentPasted0">/</div>
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</div>
<div class="FluidPluginCopy ContentPasted0">&SYSTEM</div>
<div class="FluidPluginCopy ContentPasted0"> ibrav = 0,</div>
<div class="FluidPluginCopy ContentPasted0"> celldm(1) = 8.6924328,</div>
<div class="FluidPluginCopy ContentPasted0"> !celldm(3) = 0.6433300,</div>
<div class="FluidPluginCopy ContentPasted0"> nat = 6,</div>
<div class="FluidPluginCopy ContentPasted0"> ntyp = 2,</div>
<div class="FluidPluginCopy ContentPasted0"> ecutwfc = 200,</div>
<div class="FluidPluginCopy ContentPasted0"> ecutrho = 800,</div>
<div class="FluidPluginCopy ContentPasted0"> occupations = 'fixed',</div>
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<div class="FluidPluginCopy ContentPasted0">&ELECTRONS</div>
<div class="FluidPluginCopy ContentPasted0"> mixing_beta = 0.7,</div>
<div class="FluidPluginCopy ContentPasted0"> conv_thr = 1.0d-10,</div>
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<div class="FluidPluginCopy ContentPasted0">ATOMIC_SPECIES</div>
<div class="FluidPluginCopy ContentPasted0">Ti 47.867 Ti.pz-hgh.UPF</div>
<div class="FluidPluginCopy ContentPasted0">O 15.9994 O.pz-hgh.UPF</div>
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<div class="FluidPluginCopy ContentPasted0">K_POINTS {automatic}</div>
<div class="FluidPluginCopy ContentPasted0">4 4 6 1 1 1</div>
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</div>
<div class="FluidPluginCopy ContentPasted0">CELL_PARAMETERS {alat}</div>
<div class="FluidPluginCopy ContentPasted0"> 0.982600556 0.000000000 0.000000000</div>
<div class="FluidPluginCopy ContentPasted0"> 0.000000000 0.982600556 0.000000000</div>
<div class="FluidPluginCopy ContentPasted0"> 0.000000000 0.000000000 0.629408068</div>
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</div>
<div class="FluidPluginCopy ContentPasted0">ATOMIC_POSITIONS {crystal}</div>
<div class="FluidPluginCopy ContentPasted0">Ti 0.5000000000 0.5000000000 0.0000000000</div>
<div class="FluidPluginCopy ContentPasted0">Ti 0.0000000000 0.0000000000 0.5000000000</div>
<div class="FluidPluginCopy ContentPasted0">O 0.6959241507 0.6959241507 0.5000000000</div>
<div class="FluidPluginCopy ContentPasted0">O 0.1959241507 0.8040758493 0.0000000000</div>
<div class="FluidPluginCopy ContentPasted0">O 0.8040758493 0.1959241507 0.0000000000</div>
<div class="FluidPluginCopy ContentPasted0">O 0.3040758493 0.3040758493 0.5000000000</div>
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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">! ph.x</span></div>
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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt;">&INPUTPH</span><br>
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<div class="FluidPluginCopy ContentPasted1"> tr2_ph = 1.0d-18,</div>
<div class="FluidPluginCopy ContentPasted1"> prefix = 'TiO2',</div>
<div class="FluidPluginCopy ContentPasted1"> amass(1) = 47.867,</div>
<div class="FluidPluginCopy ContentPasted1"> amass(2) = 15.9994,</div>
<div class="FluidPluginCopy ContentPasted1"> outdir = '/home/cw279/projects/def-crandles/cw279/TiO2/ph',</div>
<div class="FluidPluginCopy ContentPasted1"> epsil = .true.,</div>
<div class="FluidPluginCopy ContentPasted1"> trans = .true.,</div>
<div class="FluidPluginCopy ContentPasted1"> lraman = .true.,</div>
<div class="FluidPluginCopy ContentPasted1"> fildyn = 'TiO2.dyn',</div>
<div class="FluidPluginCopy ContentPasted1">/</div>
<div class="FluidPluginCopy ContentPasted1">0.0 0.0 0.0</div>
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! dynmat.in</div>
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&INPUT
<div class="FluidPluginCopy ContentPasted2"> fildyn = 'TiO2.dyn',</div>
<div class="FluidPluginCopy ContentPasted2"> asr = 'simple',</div>
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! dynmat.out</div>
<div class="elementToProof ContentPasted2 ContentPasted3" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">
# mode [cm-1] [THz] IR Raman depol.fact
<div class="FluidPluginCopy ContentPasted3"> 1 -165.11 -4.9500 132.3930 0.0000 0.3695</div>
<div class="FluidPluginCopy ContentPasted3"> 2 -113.43 -3.4004 91.9463 0.0000 0.6303</div>
<div class="FluidPluginCopy ContentPasted3"> 3 -113.43 -3.4004 91.9463 0.0000 0.5188</div>
<div class="FluidPluginCopy ContentPasted3"> 4 -87.89 -2.6347 0.0000 0.0000 0.2925</div>
<div class="FluidPluginCopy ContentPasted3"> 5 -0.00 -0.0000 0.0000 0.0000 0.4869</div>
<div class="FluidPluginCopy ContentPasted3"> 6 -0.00 -0.0000 0.0000 0.0000 0.3389</div>
<div class="FluidPluginCopy ContentPasted3"> 7 0.00 0.0000 0.0000 0.0000 0.3544</div>
<div class="FluidPluginCopy ContentPasted3"> 8 122.17 3.6624 0.0000 0.3837 0.7500</div>
<div class="FluidPluginCopy ContentPasted3"> 9 372.09 11.1551 0.0000 0.0000 0.7144</div>
<div class="FluidPluginCopy ContentPasted3"> 10 375.77 11.2654 3.9843 0.0000 0.3068</div>
<div class="FluidPluginCopy ContentPasted3"> 11 375.77 11.2654 3.9843 0.0000 0.4022</div>
<div class="FluidPluginCopy ContentPasted3"> 12 421.88 12.6475 0.0000 0.0000 0.7072</div>
<div class="FluidPluginCopy ContentPasted3"> 13 447.56 13.4176 0.0000 239.3889 0.7500</div>
<div class="FluidPluginCopy ContentPasted3"> 14 447.56 13.4176 0.0000 239.3889 0.7500</div>
<div class="FluidPluginCopy ContentPasted3"> 15 480.43 14.4028 14.4178 0.0000 0.5190</div>
<div class="FluidPluginCopy ContentPasted3"> 16 480.43 14.4028 14.4178 0.0000 0.7318</div>
<div class="FluidPluginCopy ContentPasted3"> 17 601.42 18.0300 0.0000 1203.1157 0.2824</div>
18 815.02 24.4338 0.0000 5.3306 0.7500<br>
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