<P>Dear matteo calandra,</P>
<P>Thanks for your instructions. I did the comparision as you said. The DOS and the xanes before occupied cutting can be comparable (I will send the files to you seperately). However, whatever i did, the xanes after occupied cutting was strange. I attached the files i used, maybe there was something error or lost information, but i never found them. </P>
<P>The strange thing was that even there are values larger than zero in the xanes before cutting, the xanes after cutting is most zero except in a narrow area in energy (x-aixs). I did not know where the values gone. </P>
<P>Thanks a lot£¬and best wishes.</P>
<P>Jiayu</P>
<P> </P>
<P>Date: Thu, 30 Sep 2010 15:50:01 +0200<BR>From: matteo calandra</P>
<P>Subject: Re: [Pw_forum] negative values in XANES (jiayudai)<BR>To: <A href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</A><BR>Message-ID:</P>
<P>Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";<BR> format="flowed"</P>
<P>Dear Jiayudai,</P>
<P> it is a bit difficult to understand what do you mean without having a<BR>picture. Maybe you can try the following for the high pressure case.<BR>You take a GIPAW pseudopotential compatible with XSPECTRA<BR>without core hole and do again the calculation without cutting occupied<BR>states but inserting your ef_r value. Then you compare your results with the<BR>corresponding projected density of states calcolated with projwfc. For <BR>corresponding I mean<BR>corresponding to the choice of your polarization (and k-vector<BR>if you are calculating the quadrupolar part).<BR>They should be the same (or very similar as probably you don't have all<BR>the same parameters in the two calculations, number of bands, broadening...)<BR>except for a prefactor along the y axis.<BR>So you can check if you are not making a mistake somewhere.</P>
<P>All the best, M.</P>
<P> </P>
<P>><BR>> Message: 3<BR>> Date: Thu, 30 Sep 2010 19:54:51 +0800<BR>> From: "jiayudai"</P>
<P>> Subject: Re: [Pw_forum] negative values in XANES<BR>> To: <A href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</A><BR>> Message-ID:</P>
<P>> Content-Type: text/plain; charset="gb2312"<BR>><BR>> Dear matteo,<BR>><BR>> Thanks for your reply to me. The "negative" means the negative <BR>> position in x-axis. And i added the "ef_r" in the input file, and <BR>> the position of the absorption is reasonable now. However, when the <BR>> pressure is high (high density), the fermi energy should be also <BR>> very high. Even i added the "ef_r", the absorption after cutting the <BR>> contribution of occupied states is only a isolated peak. In the same <BR>> case but with lower density, there is not this problem. And the <BR>> analysis of density of states for the system tells me that there <BR>> should be absorption at the position of high energy. In this case, <BR>> the absorption before occ_cut and after occ_cut is very different <BR>> (the intensity is very weak, about 10-8). So, i can not find physcal <BR>> reason to explain it. Is there also some problems in my calculation?<BR>><BR>> By the way, i changed some parameters of &occ_cut& part, but the <BR>> results were the same.<BR>><BR>> Thanks again, and best wishes.<BR>><BR>> Jiayu<BR>><BR>><BR>> Subject: Re: [Pw_forum] negative values in XANES (jiayudai)<BR>> To: PWSCF Forum<BR>><BR>> Message-ID:<BR>><BR>> Content-Type: text/plain; charset="iso-8859-1"<BR>><BR>> Matteo, thank you for taking the time to participate in the <BR>> discussion. In the future, please hit "reply" when answering a post, <BR>> rather than starting a new thread. Have all a good day - Stefano B<BR>><BR>> On Sep 30, 2010, at 9:13 AM, matteo calandra wrote:<BR>><BR>>> Dear Jiayu,<BR>>><BR>>> I assume you're using XSPECTRA to calculate Xanes K-edge.<BR>>> Maybe you can better specify what does it means "negative<BR>>> absorption". If this means that the value on the XANES intensity is negative<BR>>> then you must have some problem somewhere as the cross section<BR>>> implemented in XSPECTRA is positive definite.<BR>>><BR>>> However, from your e-mail it is not very clear if the<BR>>> absorption is positive definite (as you say) or if the energy scale<BR>>> (the x axis in the plot)<BR>>> is negative but not the X-ray absorption intensity (y-axis in the plot).<BR>>> If y is positive and x is negative, then you simply forgot<BR>>> to specify the variable<BR>>> ef_r in the XSPECTRA input file. This variable tells you the zero<BR>>> energy of the scale. From the XSPECTRA input file:<BR>>><BR>>> ef_r real(DP) <BR>>> DEFAULT=0.0<BR>>> Fermi energy in Rydberg. This value combined<BR>>> with the option cut_occupied_states can be<BR>>> used to exclude the occupied states in a<BR>>> smooth way from the final plot.<BR>>><BR>>> I hope it helps,<BR>>><BR>>> M.<BR>>><BR>>><BR>>>> Dear developers and users,<BR>>>><BR>>>> I am doing the calculation for the XANES of CHx system. There is a<BR>>>> problem that the absorption is always negative, locating at about<BR>>>> -100 eV. According to my >understanding, the absorption should be<BR>>>> positive. Besides, the fermi energy in >my systems is very high,<BR>>>> about tens of eV (high pressure). Therefore, if i used the cutoff of<BR>>>> fermi energy, the absorption should be very small. Is it<BR>>>>> reasonable? Or there is some problems in the calculations?<BR>>>><BR>>>> Thanks in advance.<BR>>>><BR>>>> Jiayu<BR>>><BR>>> ----------------------------------------------------------------<BR>>> This message was sent using IMP, the Internet Messaging Program.<BR>>><BR>>><BR>>> _______________________________________________<BR>>> Pw_forum mailing list<BR>>> <A href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</A><BR>>> <A href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A><BR>><BR>> ---<BR>> Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste<BR>> <A href="http://stefano.baroni.me">http://stefano.baroni.me</A> [+39] 040 3787 406 (tel) -528 (fax) / <BR>> stefanobaroni (skype)<BR>><BR>> La morale est une logique de l'action comme la logique est une <BR>> morale de la pens?e - Jean Piaget<BR>><BR>> Please, if possible, don't send me MS Word or PowerPoint attachments<BR>> Why? See: <A href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</A><BR>><BR>><BR>><BR>><BR>><BR>><BR>><BR>> -------------- next part --------------<BR>> An HTML attachment was scrubbed...<BR>> URL: <BR>> <A href="http://www.democritos.it/pipermail/pw_forum/attachments/20100930/c1998bf7/attachment.htm">http://www.democritos.it/pipermail/pw_forum/attachments/20100930/c1998bf7/attachment.htm</A><BR>><BR>> ------------------------------<BR>><BR>> _______________________________________________<BR>> Pw_forum mailing list<BR>> <A href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</A><BR>> <A href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A><BR>><BR>><BR>> End of Pw_forum Digest, Vol 39, Issue 57<BR>> ****************************************<BR>><BR>><BR>><BR>> ----------------------------<BR> <BR>----------------<BR>-------------------------------------------<BR>Jiayu Dai<BR>Department of Physics<BR>National University of Defense Technology, <BR>Changsha, 410073, P R China<BR>----------------------------------------- </P>