posted on 2013-04-16, 00:00authored byMarcel Giesbers, Antonius
T. M. Marcelis, Han Zuilhof
Several
simple methods are presented and evaluated to simulate
the X-ray photoelectron spectra (XPS) of organic monolayers and polymeric
layers by density functional theory (DFT) and second-order Møller–Plesset
theory (MP2) in combination with a series of basis sets. The simulated
carbon (C1s) XPS spectra as obtained via B3LYP/6-311G(d,p) or M11/6-311G(d,p)
calculations are in good agreement (average mean error <0.3 eV)
with the experimental spectra, and good estimates of C1s spectra can
be obtained via EC1s(exp) = 0.9698EC1s(theory) + 20.34 (in eV) (B3LYP/6-311G(d,p)).
As a result, the simulated C1s XPS spectra can elucidate the binding
energies of the different carbon species within an organic layer and,
in this way, greatly aid the assignment of complicated C1s XPS spectra.
The paper gives a wide range of examples, including haloalkanes, esters,
(thio-)ethers, leaving groups, clickable functionalities, and bioactive
moieties.