<div dir="ltr"><div><div><div><div><div>Dear SungHwan,<br></div>please refer to <br><a href="http://arxiv.org/pdf/1402.0486.pdf">http://arxiv.org/pdf/1402.0486.pdf</a><br></div>and<br><a href="http://urania.sissa.it/xmlui/bitstream/handle/1963/5797/turboTDDFT-CPC.pdf?sequence=1">http://urania.sissa.it/xmlui/bitstream/handle/1963/5797/turboTDDFT-CPC.pdf?sequence=1</a><br></div>for more details.<br><br></div>In the output of the postprocessing chi_1_1 is the xx component of the dynamical polarizability, chi_1_2 the xy component, etc.<br></div><div>Often chi is indicated as \alpha in the papers.<br></div>Specifically you would have<br><div><div><br>Component      energy of the perturbation      real part of chi                          imaginary<br></div><div>                      (indicated either as E or \omega)<br></div><div>chi_1_1=          0.000000000000000E+00     0.955769346791472E+01  0.000000000000000E+00<br>.........<br><br></div><div>As you correctly say the absorption spectrum is related to the imaginary part of the average of chi multiplied by E (the energy E is often<br>indicated as \omega).<br></div><div>This averaged quantity is contained in S(E). Specifically S(E) is the strength function defined as<br><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgb(255,255,255)">S(E)=2m/(\pi*e^2*\hbar) * E*Im[chi(E)], where chi has been averaged over the 3 spatial directions. <br>This definition is convenient because S(E) satisfies the f-sum rule.<br></span></div><div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgb(255,255,255)">So if you extract S(E) and plot it you will have the absorption spectrum.<br></span></div><div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgb(255,255,255)">Let me know if it's still not clear<br></span></div><div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgb(255,255,255)">Best,<br></span></div><div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;display:inline!important;float:none;background-color:rgb(255,255,255)">Dario <br style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255)"></span></div><div><br></div><div><br><br></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 19, 2016 at 4:01 PM, SungHwan Choi <span dir="ltr"><<a href="mailto:sunghwanchoi91@gmail.com" target="_blank">sunghwanchoi91@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><span style="font-size:14px">    hi, I am a newbie for turboTDDFT. Now, I ran a simple example. It was </span><span style="font-size:14px">assume. Now I have prefix.plot_chi.dat  file. then I don't know how to</span><span style="font-size:14px"> generate absorption spectrum from that file and dielectric constant values. As far as I understood, the</span><span style="font-size:14px"> absorption spectrum is related to imaginary part of average \chi value. but in the file there are </span><span style="font-size:14px">9 values</span><br style="font-size:14px"><span style="font-size:14px">         chi_1_1</span><br style="font-size:14px"><span style="font-size:14px">         chi_2_1</span><br style="font-size:14px"><span style="font-size:14px">         chi_3_1</span><br style="font-size:14px"><span style="font-size:14px">         chi_1_2</span><br style="font-size:14px"><span style="font-size:14px">         chi_2_2</span><br style="font-size:14px"><span style="font-size:14px">         chi_3_2</span><br style="font-size:14px"><span style="font-size:14px">         chi_1_3</span><br style="font-size:14px"><span style="font-size:14px">         chi_2_3</span><br style="font-size:14px"><span style="font-size:14px">         chi_3_3</span><br style="font-size:14px"><span style="font-size:14px">This is 3*3*3 tensor. how do I get an absorption spectrum and dieletric constant values? by the way S(E) means what? </span><div><br style="font-size:14px"><span style="font-size:14px">Sincerely</span><span class="HOEnZb"><font color="#888888"><br style="font-size:14px"><span style="font-size:14px">Sunghwan Choi</span><br></font></span></div></div>
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