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I've been studying the electronic structure of platinum nanoparticles using DFT and have a question about comparing my calculated density of states (DOS) with experimental valence band spectra.

I recently came across a paper (Phys.Chem.Chem.Phys., 2017, 19, 6013) that investigates the oxidation states of platinum nanoparticles of similar sizes using near ambient pressure hard X-ray photoelectron spectroscopy (NAP-HAXPES). The authors observed a decrease in the density of electronic states near the Fermi energy for smaller platinum nanoparticles at higher voltages, which they attributed to the oxidation of the nanoparticles.

However, when I calculated the DOS for a model system (cluster in vacuum, this is DFT) of platinum nanoparticles with varying oxygen ratios, I found an important increase in the density of states around the same energy range as the oxygen ratio increased.

I am not an experimentalist, and while I am aware about thousands of reasons why experiments would give different results in practice, I am wondering if one is even able to compare these two graphs in theory. It is my understanding that the intensity from the NAP-HAXPES measurement should be proportional to the Density of State?

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  • $\begingroup$ If I understood correctly, the experimental oxidation is due to both applied voltage and oxygen. Is this the same in your calculations? $\endgroup$
    – Paul Kolk
    Commented Jun 7 at 13:11
  • $\begingroup$ @PaulKolk No, my calculations are oxidized platinum nanoparticle centered in a vacuum box, this is very far from any kind of electrochemical setup, mainly every electric effects due to charge screening will be missing, etc... This is a kind of explanation that I aim to provide in my manuscript, but first I would like to know if these two graphs are even comparable in principle. $\endgroup$
    – Okano
    Commented Jun 7 at 13:29
  • $\begingroup$ Oxidation by oxygen is one effect, interaction with oxide ions is another. As you provide more oxide ions in your theory than really present, the result is expected to differ a lot. $\endgroup$
    – Paul Kolk
    Commented Jun 7 at 13:47
  • $\begingroup$ @PaulKolk Mmmh, I am not sure that I understand your point, in the calculations oxygen atoms are partially charged not pure ions, do you mean that because of the lack of charge effects, they will be wrong? $\endgroup$
    – Okano
    Commented Jun 7 at 14:09
  • $\begingroup$ For a given oxidation state of the platinum cluster, the number of oxygen atoms changes the densities of states, I think. Even if they are not 2- ions. $\endgroup$
    – Paul Kolk
    Commented Jun 7 at 20:47

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