Results containing 0 as Raman intensities

[eamouj78]

Dear all,

I have been using the QERAMAN code for some time now. Recently, I am want to calculate the Raman intensities of a 72 atom Carbon structure. Due to this large system, the 'dvec' and 'elph' files are large (To have an idea, the 'elph' file is ~ 1.1 GB). Everything ends perfectly well. However when I execute the Raman, I get everything '0'

"Raman tensor
iel = 1
imode 1
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
imode 2
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
imode 3
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
imode 4
"

and
" 0.0300 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
4.9562 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
9.8823 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
14.8085 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
19.7347 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
24.6608 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
29.5870 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
34.5132 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
39.4393 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
44.3655 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
49.2917 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
54.2178 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
59.1440 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
64.0701 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
68.9963 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
73.9225 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000 0.00000000E+000
"

What is the Reason for this behavior? Is it memory?

Thanks in advance

[nguyen-group]

Hi,

I also did not try with such a big system. How much of the k-points did you use for scf.in?
If it is small, it might not cover the energy eigenvalue at the resonance condition; then, everything might become zero even if we have non-zero for electron-phonon and electron-photon matrix elements.

Best all,
Nguyen

[Aldi-Saraiva]

Dear @eamouj78, I’ve experienced a similar issue when calculating a semiconductor without a smearing parameter. Although the SCF cycle converges, QERaman seems to treat the system as non-insulating, resulting in a zero Raman tensor. While I’m not certain if this is the case for your system, it might be worth checking.