Thanks to Matteo Calandra for his answers. Regarding the Fermi level, I have now an additional question based on an example we are dealing with. With a preliminar run of XSpectra I see a Fermi energy of -0.259, so I use this value for ef_r in following calculations. If I include negative energies (say -30 eV, with respect to this one) in the input file then in the resulting spectrum I see a *sharp* peak at about -5 eV.
Now, if levels at negative energy should be all occupied, how can it result such an evident absorption peak? Is it related to the "cut_occ_states" option? By default it is .false. What does this mean exactly? Thanks again for your help. Cristian > (1) is the energy range (xemin,xemax) referred to the Fermi energy > > of the preliminar scf calculation? > > No, it is referred to the Fermi level given in input in the xspectra > file (input variable ef_r in the input_xspectra namelist. This means > that if you do not specify the Fermi level then ef_r=0.0 and > they are referred to the energy zero of the preliminary scf run. -- ___________________________________________________ Cristian Degli Esposti Boschi CNR, CNISM, Unita' di Ricerca di Bologna, c/o Dipartimento di Fisica, Universita' di Bologna viale Berti-Pichat, 6/2, 40127, Bologna, Italia tel. ++39 051 2095114 fax ++39 051 2095113 e-mail: cristian.degliesposti -AT- unibo.it web: http://www.df.unibo.it/fismat/theory ___________________________________________________