[QE-users] [SPAM] Re: Dielectric function and absorption with Lanczos

[José Xavier]

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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