Dear Guido Fratesi, Thank you so much for the explaination. Now I understand how to calculate the xas for the metalic system. Best, Cheng
2012/6/27 Guido Fratesi <fratesi at mater.unimib.it>: > Dear Cheng, > > xspectra can handle metal systems: see for example PHYSICAL REVIEW B 80, > 075102 (2009) fig.3. > > The Fermi level is taken as the zero of the spectrum, and might be used > to cut and remove the spectrum below E_F. By editing the value of ef_r > in input you should obtain the same spectrum, only shifted at different > energies. > > What is the Fermi level for your insulator? Notice, it will depend on > the choice of occupation functions. So, probably xspectra was giving you > the HOMO, while if you set smearing with gaussian functions you will get > something close to (HOMO+LUMO)/2 (depending on occupied/empty DOSs). > Indeed your E_F in this case is higher. In principle, for systems at > T=0, anything in between the HOMO and the LUMO is reasonable. The > resulting spectrum will not change but for the reference energy, it > suffices that you do things consistently. > > Hope this helps, > Guido > > On 06/26/2012 03:25 PM, ??? wrote: >> Dear all, >> I have installed QE5.0 with xpectra installed. >> I just tested the diamond example and it runs through. >> In this example, the diamond is treated as insulator.(Of course!) >> In the second step, xspectra.x can get the Fermi level of 0.94038144 >> Ry (12.8 eV). >> If I set the system as metal with occupation "smearing", the >> xspectra.x will complained when I try to get the Fermi level. >> The error message is as below: >> ? Metallic case >> >> >> ? >> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% >> ? ? ? from input : error # ? ? ? ? 1 >> ? ? ? Read fermi level from scf/nscf output >> ? >> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% >> >> ? ? ? stopping ... >> >> But the Fermi level printed in the scf output file is 15.88 eV. >> My first question is why the two fermi level value are different so much. >> Second question is whether xspectra.x can calculate the XAS for metalic >> system? >> Thank you in advance. >> Best, >> > > -- > Guido Fratesi > > Dipartimento di Scienza dei Materiali > Universita` degli Studi di Milano-Bicocca > via Cozzi 53, 20125 Milano, Italy > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- Y. C. Cheng Department of Physics Nanjing University Nanjing 210093 P. R. China Tel: 86-25-83592907 Email: yccheng.nju at gmail.com
