For the best of my knowledge, the absorption (excitation) energies calculations (using Gaussian) are performed on outer shell electrons therefore we obtain "simulated UV-Vis spectrum". But I need to calculate energies of core electrons so that I can obtain simulated X-ray spectrum. Anyone knows how to do that??????
Dear Muhammad Khattab ,
please have a look at the NIST XCOM database.
https://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html
https://www.nist.gov/pml/xcom-photon-cross-sections-database
From here you can download the energy dependence of the x-ray mass-attenuation coefficent.
You are also able to directly download the XCOM program, and more over, you can create your own photon energy scale.
So get familiar with XCOM.
Binding energies of core level electrons for the elements are listed in:
https://xdb.lbl.gov/Section1/Sec_1-1.html
Click on the blue coloured' PDF version of this table' button...
and
X-ray emission line are listed in:
http://xdb.lbl.gov/Section1/Sec_1-2.html
Click on the blue coloured 'Table1-2( pdf format)' button...
You may cross check your results from Gaussian software with the XCOM output.
But, may be that I have misinterpreted your question...
good luck
Could you detail what experiment you want to model?
If you are not interested in eV accuracy, but just want to have a "qualitative plot", the core electron spectrum can be calculated as the sum of the electron spectra of the individual atoms. Then you can essentially use a Hartree-Fock calculation and take the overlaps of the core orbitals with any of the unoccupied orbitals of the atoms (or look up in a database) and you are done.
Is this sufficient, or do you want to model something more advanced, like a XANES spectrum?
Thanks Ulf.......I need to calculate simulated X-ray absorption spectrum of benzimidazole derivative
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