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<p>Dear Prem,<br>
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<p>Please do not forget to write your affiliation.<br>
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<div>> Dear All,<br>
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> I am a new user of QE and interested to calculate the optical absorption spectra in atomic level using > TDDFT code. I have checked the ecut & ecutfock convergence and also relaxed the structure. I can understand so far what is going on. But when I am running
turbo_lanczos.x and turbo_davidson.x, I am getting output but how can I check that my calculation is correct ?? </div>
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<div style="color: rgb(33, 33, 33);">There is a reference data provided with the examples for the TDDFPT package. <br>
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<div style="color: rgb(33, 33, 33);">You may compare your converged spectra with the experimental ones and with other theoretical spectra in the literature.<br>
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<div style="color: rgb(33, 33, 33);">> After running turbo_davidson.x, I am getting a file named as "CH4.plot". If I am plotting it using xmgrace, it is showing the x-axis in Ry scale but that I want in eV ??<br>
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If you use turbo_davidson.x, plot the second column of CH4.plot (labeled as "total", oscillator strength S(E)) as a function of the first column (energy E in Ry). In xmgrace you can easily do a rescaling of the axes: in your case just make a conversion of the energy
from Ry to eV by multiplying by 13.6.</div>
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<div style="color: rgb(33, 33, 33);">If you use turbo_lanczos.x, you will obtain a file "<span style="font-variant-ligatures: no-common-ligatures">CH4.plot_chi.dat</span>". This file contains an information about the <span style="font-variant-ligatures: no-common-ligatures">dipole
polarizability tensor</span> (<span style="font-variant-ligatures: no-common-ligatures">chi_i_j</span>) and about the <span style="font-variant-ligatures: no-common-ligatures">oscillator strength</span> S(E) which is: <span style="font-size: 12pt; font-variant-ligatures: no-common-ligatures;">S(E)
~ E * sum_i Im[ chi_i_i(E) ]. </span><span style="font-size: 12pt;">Extract the oscillator strength "S(E)</span><span style="font-size: 12pt;">"
</span><span style="font-size: 12pt;">from this file using the grep</span><span style="font-size: 12pt;"> </span><span style="font-size: 12pt;">command, a</span><span style="font-size: 12pt;">nd then plot S(E</span><span style="font-size: 12pt;">) as a function
of E which is the absorption </span><font color="#212121" style="font-size: 12pt;">spectrum.</font></div>
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<div style="color: rgb(33, 33, 33);">The two codes (Lanczos and Davidson) must give you the same absorption spectrum (when both are converged). More details can be found in this paper: X. Ge et al., <span style="font-variant-ligatures: no-common-ligatures">Computer
Physics Communications</span>, 185, 2080 (2014).<br>
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<font color="#212121">> Thanks,</font><br>
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<font color="#212121">> Prem</font><br>
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<div dir="ltr" style="color: rgb(33, 33, 33);">HTH<br>
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<div dir="ltr" style="color: rgb(33, 33, 33);">Regards,<br>
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<div dir="ltr" style="color: rgb(33, 33, 33);">Iurii<br>
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<font color="808080" size="3" face="'Times New Roman', Times, serif">--<br>
Dr. Iurii Timrov<br>
Postdoctoral Researcher<br>
Swiss Federal Institute of Technology Lausanne (EPFL<font color="808080"><font face="'Times New Roman', Times, serif">)</font></font></font></div>
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<font color="808080" size="3" face="'Times New Roman', Times, serif">Laboratory of Theory and Simulation of Materials <font color="808080"><font face="'Times New Roman', Times, serif">(THEOS)</font></font></font><font color="808080" size="3" face="'Times New Roman', Times, serif"><br>
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<font color="808080" size="3" face="'Times New Roman', Times, serif">Lausanne, Switzerland<br>
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