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Dear QE users,</div>
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I am trying to calculate binding energy shifts of N 1s core electrons for comparison with XPS spectra for nitrogen-containing system. For that purpose, I am using two PPs from the QE library: N.pbe-n-rrkjus_psl.1.0.0.UPF and the corresponding 1s core-hole one
N.star1s-pbe-rrkjus.UPF.<span> </span><br>
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The standard procedure involves calculating the energy of a system with N electrons and comparing with the equivalent system with N-1 electrons, achieved by using the core hole PP, so that a simple definition of binding energy (energy required to remove the
electron) might be BE=E(N-1)-E(N). The problem I am having is that I am getting negative values, I suspect due to some simple error I have overlooked.</div>
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As an example, I attach the input for a N2 molecule, relaxed without core-hole, and that now includes a core-hole in one of the atoms. The binding energy predicted by this configuration is (rounding numbers):</div>
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BE=E(N-1)-E(N)=-51.47Ry-(-40.87Ry)=-10.62 Ry=-144.53 eV<br>
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So even if the sign was flipped the absolute value is very far from the ~400eV of the N1s XPS peak.<span> </span><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; background: var(--white);">Any help is appreciated.</span></div>
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Kind regards,</div>
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Carlos Ayestarán Latorre</div>
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PhD student</div>
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Department of Mechanical Engineering</div>
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Imperial College London</div>
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