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Does anyone have any experience simulating Raman spectra in Quantum ESPRESSO? Following the example 15 that comes with QE, I have attempted to simulate the Raman spectrum of MgO. I know the lraman flag must be set to .true., and I have used norm-conserving pseudopotentials. My code runs without error, and prints the IR activities, but the Raman activities are missing.

Does anyone know how to make QE print the Raman activities?

Edit: I should also mention that I'm running version 7.0 of Quantum ESPRESSO.

Edit 2: Following the example 15, I'm able to simulate the Raman intensities of bulk Si. Does anyone know why QE will print the intensities for bulk Si but not MgO? Do I need to treat the case of MgO differently? I'm attaching my input files below. Any help would be greatly appreciated.

pw.x calculation:

    &CONTROL
      calculation = 'scf',
      prefix = 'MgO',
      outdir = '/home/cw279/',
      pseudo_dir = '/usr/share/espresso/pseudo',
    /

    &SYSTEM
      ibrav = 2,
      celldm(1) = 8.043589,
      nat = 2,
      ntyp = 2,
      ecutwfc = 80.0,
      occupations = 'fixed',
    /

    &ELECTRONS
    /

    ATOMIC_SPECIES
      Mg  24.305   Mg.pz-hgh.UPF
      O   15.999   O.pz-hgh.UPF

    K_POINTS {automatic}
      4 4 4  1 1 1

    ATOMIC_POSITIONS {crystal}
      Mg  0.000000  0.000000  0.000000
      O   0.500000  0.500000  0.500000

ph.x calculation:

    &INPUTPH
      tr2_ph = 1.0d-18,
      prefix = 'MgO',
      amass(1) = 24.305,
      amass(2) = 15.999,
      outdir = '/home/cw279/',
      epsil = .true.,
      trans = .true.,
      lraman = .true.,
      fildyn = 'MgO.dyn',
    /
    0.0 0.0 0.0

dynmat.x calculation:

    &INPUT
      fildyn = 'MgO.dyn',
      asr = 'crystal',
    /
$\endgroup$
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  • $\begingroup$ Did you successfully followed/finished the tutorial? $\endgroup$
    – Camps
    May 16, 2022 at 20:59
  • $\begingroup$ Thank you for your reply. The only tutorial I've seen on Raman simulations in QE is this one here: blog.larrucea.eu/compute-ir-raman-spectra-qe which I did follow, and which seems identical to example 15. When I copy the input files on that tutorial verbatim and run them, the Raman activities still don't print. $\endgroup$
    – CW279
    May 16, 2022 at 22:36

1 Answer 1

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It would seem that if a crystal system has no Raman-active modes, QE simply won't print out the Raman intensities. To verify this, I tried to simulate the Raman activity of $\ce{NaCl}$ (also a member of the m3m point group, like $\ce{MgO}$), and again, QE didn't print anything. This would also explain why the intensities for $\ce{ZnO}$ (m3m) in example 15 didn't print either.

However, QE will print the Raman intensities for $\ce{Si}$ (diamond) and $\ce{GaAs}$ (zincblende). I will leave below my input files for $\ce{GaAs}$.

If I'm incorrect that QE doesn't print the Raman intensities for a Raman-inactive point group, please let me know!


GaAs input files:

pw.x calculation:

    &CONTROL
      calculation='scf',
      restart_mode='from_scratch',
      prefix='GaAs'
      pseudo_dir = '/usr/share/espresso/pseudo',
      outdir='/home/cw279/',
    /

    &SYSTEM
      ibrav = 2,
      celldm(1) = 10.4455,
      nat = 2,
      ntyp = 2,
      ecutwfc = 60.0,
      occupations = 'fixed',
    /

    &ELECTRONS
    /

    ATOMIC_SPECIES
      Ga  69.723   Ga.pz-hgh.UPF   ! QE throws error unless PP is LDA
      As  74.9216  As.pz-hgh.UPF   ! and norm-conserving

    K_POINTS {automatic}
      4 4 4  1 1 1

    ATOMIC_POSITIONS {crystal}
      Ga  0.000000 0.000000 0.000000
      As  0.250000 0.250000 0.250000

ph.x calculation:

    &INPUTPH
      tr2_ph = 1.0d-19,
      prefix = 'GaAs',
      amass(1) = 69.723,
      amass(2) = 74.92160,
      outdir = '/home/cw279',
      epsil = .true.,
      trans = .true.,
      lraman = .true.,
      fildyn = 'GaAs.dyn',
    /
    0.0 0.0 0.0

dynmat.x calculation:

    &INPUT
      fildyn = 'GaAs.dyn',
      asr = 'simple',
      q(1) = 1.0,        !to correct for LO-TO splitting
      q(2) = 0.0,
      q(3) = 0.0,
    /
$\endgroup$
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  • $\begingroup$ Can anyone explain to me what they are or where these values come from? ``` amass(1) = 69.723, amass(2) = 74.92160``` $\endgroup$ Mar 2 at 18:26
  • $\begingroup$ @CarolineSantos Those are the masses of the Ga and As ions in units of amu. $\endgroup$
    – CW279
    Mar 3 at 0:01

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