[QE-users] Dielectric function and absorption with Lanczos

[Iurii TIMROV]

Dear Jose,


> My first question is, in this situation, should I create a supercell?


Probably yes, I do not know this system so I cannot answer certainly.


> I believe the Real and Imaginary parts of the Dielectric function are columns 3 and 4.


Yes


> How can I use these data to plot a graph for the different directions ([001] [010][100])?


What is contained in plot_chi is chi_1_1 (=chi_xx), chi_2_1 (=chi_yx), etc. These matrix elements can be used to plot the graphs that you want.


HTH


Iurii



--
Dr. Iurii TIMROV
Senior Research Scientist
Theory and Simulation of Materials (THEOS)
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: José Xavier <jxln_karate at yahoo.com.br>
Sent: Tuesday, April 25, 2023 2:57:57 AM
To: Quantum ESPRESSO Users Forum; Iurii TIMROV
Subject: Re: Dielectric function and absorption with Lanczos

Dear Dr. Timrov,

Thanks for your answer.

I was trying to perform the calculation with Si as a test.. Now I'm trying to perform the calculation with the crystal I'll work with... I want to reproduce the paper "DFT calculations of the structural, electronic, optical and vibrational properties of anhydrous orthorhombic L-threonine crystals" but with another amino acid (4 molecules in the crystal). My first question is, in this situation, should I create a supercell?

I applied the same parameters in the SCF (gamma k-points), Lanczos, and Spectrum. In the end, I got the plot_S and plot_chi files. In the former, it has the column omega(Ev) and Oscillator strength. In the second, there's a kind of matrix:
                             \hbar \omega(eV)          Re(chi) (e^2*a_0^2/eV)       Im(chi) (e^2*a_0^2/eV)
     chi_1_1=  0.000000000000000E+00  0.251513541607848E+02  -.000000000000000E+00
     chi_2_1=  0.000000000000000E+00  0.289682796308743E-01  -.000000000000000E+00
     chi_3_1=  0.000000000000000E+00  -.627424728613613E+01  0.000000000000000E+00
     chi_1_2=  0.000000000000000E+00  0.287160382756907E-01  -.000000000000000E+00
     chi_2_2=  0.000000000000000E+00  0.316761800714172E+02  -.000000000000000E+00
     chi_3_2=  0.000000000000000E+00  -.136008122822626E-01  0.000000000000000E+00
     chi_1_3=  0.000000000000000E+00  -.627868400613771E+01  0.000000000000000E+00
     chi_2_3=  0.000000000000000E+00  -.132116766101710E-01  0.000000000000000E+00
     chi_3_3=  0.000000000000000E+00  0.250771241870414E+02  -.000000000000000E+00

I believe the Real and Imaginary parts of the Dielectric function are columns 3 and 4. How can I use these data to plot a graph for the different directions ([001] [010][100])?




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