# [Pw_forum] Several questions about the xspectra code in QE

Zhufeng Hou zfhou at fudan.edu.cn
Wed Apr 28 04:25:47 CEST 2010

Dear all,

For the usage of xspectra code, I have the following questions to be clear.
1) When one does the self-consistent calculations of system with core-hole, should the keyword "nelec" be specified explicitly with a value (N or N+1, N is the total electrons of this system without core-hole)? I did a test calculation without the keyword "nelec" in the inptu file for the system with core-hole, and found that the value of total electrons is automatically determined to be N+1.

2). In the examples provided with the distribution of QE (4.1.1 version), several cases such as NiO and SiO2  demonstrated the calculations only for the XAS spectra of systems without core-hole. Why not show the calculations with core-hole? If one wants to do exercises for reproducing the the results presented in the related  papers (PRB80,075102(2009) and PRB79, 045118 (2009)), should the systems with core-hole be calculated?

3) From the formula of the dipolar cross section (e.g., eq.(27) in PRB80,075102(2009)),  it seems that the angle \theta between the c axis and the polarization vector is controlled by the values of keywords "xkev(1:3)" and "xepsilon(1:3)". Is my understanding correct?

Best regards
Zhufeng