Matteo, thank you for taking the time to participate in the discussion. In the future, please hit "reply" when answering a post, rather than starting a new thread. Have all a good day - Stefano B
On Sep 30, 2010, at 9:13 AM, matteo calandra wrote: > Dear Jiayu, > > I assume you're using XSPECTRA to calculate Xanes K-edge. > Maybe you can better specify what does it means "negative > absorption". If this means that the value on the XANES intensity is negative > then you must have some problem somewhere as the cross section > implemented in XSPECTRA is positive definite. > > However, from your e-mail it is not very clear if the > absorption is positive definite (as you say) or if the energy scale > (the x axis in the plot) > is negative but not the X-ray absorption intensity (y-axis in the plot). > If y is positive and x is negative, then you simply forgot > to specify the variable > ef_r in the XSPECTRA input file. This variable tells you the zero > energy of the scale. From the XSPECTRA input file: > > ef_r real(DP) DEFAULT=0.0 > Fermi energy in Rydberg. This value combined > with the option cut_occupied_states can be > used to exclude the occupied states in a > smooth way from the final plot. > > I hope it helps, > > M. > > >> Dear developers and users, >> >> I am doing the calculation for the XANES of CHx system. There is a >> problem that the absorption is always negative, locating at about >> -100 eV. According to my >understanding, the absorption should be >> positive. Besides, the fermi energy in >my systems is very high, >> about tens of eV (high pressure). Therefore, if i used the cutoff of >> fermi energy, the absorption should be very small. Is it >>> reasonable? Or there is some problems in the calculations? >> >> Thanks in advance. >> >> Jiayu > > ---------------------------------------------------------------- > This message was sent using IMP, the Internet Messaging Program. > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20100930/c1998bf7/attachment-0001.htm
