Hi, I am a beginner in this subject, but as I understood it is possible to predict (with certain accuracy) the XPS spectra of an organic molecule using NBO package from GAUSSIAN 09
My question is, in the output or chk file, where can I find the full X (eV) and Y values (Intensity in a.u.), so that I can trace the theoretical curve, for example of the C 1s?. I know where the Binding Energies of each atom can be calculated, but not the hole range of the spectrum.
For instance, using GaussView I visually locate the HOMO and LUMO of C15 (for example), but I wonder where is this important imformation located in the out or chk file
Thanks
While I don't see why you would use the NBO package since you don't need bond orders for XPS analysis, you can get to an interpretation from your canonical orbital energies:
Extract the C1s area of your orbital energy file and check their distribution. Then you have the relative shifts of your components within the molecule. Since you don't have effects of a conduction process going on as it would be in graphite, you can "simulate" a primitive XPS by just putting a Lorentzian/Gaussian/pseudo-Voigt over it and play with the width of it; a former colleaugue of mine used a simple Linux shell script for that, but that was for Turbomole output files, so not helpful for you. Please note that depending on the used functional and basis set, there will be an offset on your absolute values.
On a Koopmans' Theorem level, you are done at this point.
If you want a bit more physics to be accounted for in your intensities, the "final state" or "frozen orbital" approximation would be the next level of escalation:
https://www.researchgate.net/post/How-to-perform-Frozen-Orbital-Approximation-to-calculate-relative-Intensities-in-XPS
Thank you Jürgen Weippert , I think I confused the term "NBO package". I will try to find the area in the energy file. By any chance, could you show me a sample?
Thank you in advance
I never used Gaussian for XPS referencing, so unfortunately I can't, my Gaussian experiences are somewhat back in time. For Turbomole I could show you, but I don't think that's helpful for you.
Calculation of XPS using Koopmans theory and Gaussian09 can be conducted using the following method.
The following is written in Japanese, but you can translate using google translation or deepL.
https://www.jstage.jst.go.jp/article/tanso/2015/269/2015_15703/_pdf/-char/en
The related reserach can be check from the following website and you tube.
https://youtu.be/c69-9EWiQ64
http://chem.tf.chiba-u.jp/~y-yamada/publication.htm
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