<div dir="ltr">Hi Everyone,<div> I am James Johns from the University of Minnesota Chemistry Department. I was trying to assign the modes in an experimental Raman spectrum by comparison to calculations using symmetry and the predicted off-resonance intensity (the material contains Mo and Te). The intensities that I calculated seemed to be nonsense, so I tried looking at two simpler systems, monolayer MoS2 and monolayer MoTe2. When I calculate the Raman intensities for MoS2, I get reasonable agreement with experiment (two primary peaks, and E1 and A1, with similar intensities (A 2:1 ratio). When I swap to MoTe2, which has a similar first order Raman spectrum (2 peaks, 1 E1 and one A1 with similar intensity) I see that the symmetries are correct, but the A1 mode is much more intense than the E1 pair (816 A^4/amu vs 8 A^4/amu). I thought his might be an issue with the Te pseudopotential, so I tried two others (a Troullier-Martin and a Hartwigsen-Goedeker-Hutter pseudopotential) and while the numbers changed, the pattern didn't. </div><div>When I try to calculate the Raman intensities for my actual system, I always see a similar trend where one mode is calculated to be vastly more intense than the others. I've copied the output of my dynmat input files and the input files for pw.x, ph.x, and dynmat.x below, but I wanted to ask if anyone had any thoughts on why the LDA MoS2 intensity would be approximately correct, but not MoTe2?</div><div><br></div><div>Thanks,<br>James Johns</div><div><br></div><div><br></div><div><br></div><div>MoTe2 Dynmat Output::</div><div><br></div><div><div><br></div><div># mode [cm-1] [THz] IR Raman depol.fact</div><div> 1 -0.00 -0.0000 0.0000 5.7100 0.7500</div><div> 2 -0.00 -0.0000 0.0000 5.7662 0.7500</div><div> 3 0.00 0.0000 0.0000 0.0562 0.7500</div><div> 4 119.78 3.5908 0.0000 0.5311 0.7500</div><div> 5 119.78 3.5908 0.0000 0.5311 0.7500</div><div> 6 174.02 5.2171 0.0000 816.7296 0.1155</div><div> 7 239.25 7.1726 5.0484 8.2978 0.7500</div><div> 8 239.25 7.1726 5.0484 8.2978 0.7500</div><div> 9 296.36 8.8846 0.0096 0.0000 0.1201</div><div><br></div><div><br></div><div>MoS2 Dynmat Output:</div><div><div><br></div><div># mode [cm-1] [THz] IR Raman depol.fact</div><div> 1 -0.00 -0.0000 0.0000 0.4655 0.7500</div><div> 2 0.00 0.0000 0.0000 0.0026 0.7500</div><div> 3 0.00 0.0000 0.0000 0.4645 0.7500</div><div> 4 287.40 8.6159 0.0000 0.2081 0.7500</div><div> 5 287.40 8.6159 0.0000 0.2081 0.7500</div><div> 6 390.61 11.7103 1.4530 73.6968 0.7500</div><div> 7 390.61 11.7103 1.4530 73.6968 0.7500</div><div> 8 406.95 12.2000 0.0000 461.7732 0.1076</div><div> 9 474.79 14.2337 0.0043 0.0000 0.1812</div><div>#######################################################</div></div><div>#######################################################</div><div><br></div><div>Input Files for MoS2</div><div>PW.X Input</div><div><div> &control</div><div> calculation= 'relax'</div><div> nstep = 75</div><div> etot_conv_thr= 1.0d-7</div><div> forc_conv_thr= 1.0d-6</div><div> prefix='MoS2.PBE'</div><div> outdir='/home/johnsj/jjohns/MoS2_Phonon'</div><div> pseudo_dir='/home/johnsj/jjohns/Psuedo/PSEUDOPOTENTIALS_NC'</div><div> !tefield=.true.,</div><div> !dipfield=.true.,</div><div>/</div><div> &system</div><div> ibrav= 4, celldm(1)=5.95799552 , celldm(3)=14.5844 nat= 3, ntyp=2, nbnd=50,</div><div> ecutwfc=60.0,</div><div> occupations='fixed'</div><div> !smearing='gauss'</div><div> !degauss=0.01</div><div> !vdw_corr= 'ts'</div><div> !edir=3</div><div> !emaxpos = 0.05</div><div> !eopreg =0.1</div><div> !eamp=0</div><div> !nspin=2</div><div> !starting_magnetization(2)=0.5</div><div> !input_dft='HSE'</div><div> !nqx1=1, nqx2=1, nqx3=1</div><div>/</div><div> &electrons</div><div>/</div><div> &ions</div><div>/</div><div> &cell</div><div> !cell_dofree='2Dxy'</div><div>/</div><div><br></div><div>ATOMIC_SPECIES</div><div> S 32.065 S.pz-n-nc.UPF</div><div> Mo 95.94 Mo.pz-n-nc.UPF</div><div><br></div><div>ATOMIC_POSITIONS crystal</div><div>S 1/3 2/3 0.4642</div><div>Mo 2/3 1/3 0.5</div><div>S 1/3 2/3 0.5358</div><div><br></div><div>K_POINTS automatic</div><div>15 15 1 0 0 0</div></div><div><br></div><div><br></div><div><br></div><div><br></div><div>PH.X Input</div><div><div>phonons of MoS2 at Gamma</div><div> &inputph</div><div> tr2_ph=1.0d-14</div><div> prefix='MoS2.PBE'</div><div> outdir='/home/johnsj/jjohns/MoS2_Phonon'</div><div> fildyn='MoS2.dynG'</div><div> lraman=.true.</div><div> asr=.true.</div><div> epsil=.true.</div><div> verbosity='high',</div><div> /</div><div>0.0 0.0 0.0</div></div><div><br></div><div><br></div><div>Dynmat.x Input</div><div><div> &input</div><div>fildyn='MoS2.dynG'</div><div>asr='crystal'</div><div>q=0.0 0.0 0.0</div><div>filxsf='MoS2.xsf'</div><div>/</div></div><div>#####################################################</div><div>#####################################################</div><div><br></div><div>Input Files for MoTe2</div><div><div><br></div><div> &control</div><div> calculation= 'relax'</div><div> nstep = 75</div><div> etot_conv_thr= 1.0d-7</div><div> forc_conv_thr= 1.0d-6</div><div> prefix='MoTe2.PBE'</div><div> outdir='/home/johnsj/jjohns/MoS2_Phonon'</div><div> pseudo_dir='/home/johnsj/jjohns/Psuedo/PSEUDOPOTENTIALS_NC'</div><div> !tefield=.true.,</div><div> !dipfield=.true.,</div><div>/</div><div> &system</div><div> ibrav= 4, celldm(1)=6.64030863 , celldm(3)=14.5844 nat= 3, ntyp=2, nbnd=50,</div><div> ecutwfc=60.0,</div><div> occupations='fixed'</div><div> /</div><div> &electrons</div><div>/</div><div> &ions</div><div>/</div><div> &cell</div><div> !cell_dofree='2Dxy'</div><div>/</div><div><br></div><div>ATOMIC_SPECIES</div><div> Te 127.6 Te.pz-n-nc.UPF</div><div> Mo 95.94 Mo.pz-n-nc.UPF</div><div><br></div><div>ATOMIC_POSITIONS crystal</div><div>Te 1/3 2/3 0.4642</div><div>Mo 2/3 1/3 0.5</div><div>Te 1/3 2/3 0.5358</div><div><br></div><div>K_POINTS automatic</div><div>15 15 1 0 0 0</div></div><div><br></div><div>PH.X Input</div><div><div> phonons of MoTe2 at Gamma</div><div> &inputph</div><div> tr2_ph=1.0d-14</div><div> prefix='MoTe2.PBE'</div><div> outdir='/home/johnsj/jjohns/MoS2_Phonon'</div><div> fildyn='MoTe2.dynG'</div><div> lraman=.true.</div><div> asr=.true.</div><div> epsil=.true.</div><div> verbosity='high',</div><div> /</div><div>0.0 0.0 0.0</div></div><div><br></div><div>DYNMAT.X Input</div><div><div> &input</div><div>fildyn='MoTe2.dynG'</div><div>asr='crystal'</div><div>q=0.0 0.0 0.0</div><div>filxsf='MoTe2.xsf'</div><div>/</div></div><div>################################################</div><div>################################################</div><div><br></div><div><br></div><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div>James E. Johns</div><div>Assistant Professor</div><div>Department of Chemistry</div><div>University of Minnesota</div><div>207 Pleasant St.</div><div>Minneapolis, MN 55455</div><div><a href="http://www.chem.umn.edu/groups/johns/index.html" target="_blank">http://www.chem.umn.edu/groups/johns/index.html</a><br></div></div></div>
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