# Raman Spectra in Quantum Espresso

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',
/

• Did you successfully followed/finished the tutorial?
– Camps
May 16 at 20:59
• 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. May 16 at 22:36

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,
/