Theoretical X-ray photoelectron spectra of polymers by deMon DFT calculations using the model dimers

Core-electron spectra of 15 polymers [(CH2CH2)(n) (PE), (CH2CH(CH3))(n) (PP), (CH2CH2NH)(n) (PEI), (CH2CH2O)(n) (PEG), (CH2CH(OCH3))(n) (PVME), (CH2CHF)(n) (PVF), (CH2CF2)(n) (PVDF), (CF2CF2)(n) (PTFE), (CH2CH(CN))(n) (PAN), (CH2C(CH3)(CN))(n) (PMAN), (CH2CH2S)(n) (PETHS), (CH2CHCl)(n) (PVC), (CH2CCl2)(n) (PVDC), (Si(CH3)(2))(n) (PDMS), (Si(CH3)(2)O)(n) (PDMSO)], and valence photoelectron spectra (XPS) of the six polymers (PP, PEI, PAN, PMAN, PVME, PTFE) were obtained by deMon density-functional theory (DFT) calculations using the model dimers. The core-electron spectra were simulated with the Gaussian lineshape functions with fixed linewidths of 0.5, and 1.0 eV for each C1sd, and (N1s, O1s, F1s) MO value, respectively, and calculated Al-K alpha Valence photoelectron spectra were obtained using Gaussian lineshape functions of an approximate linewidth (0.08I(k)): I-k(I-FL) = I-k’ - WD, as indicated in previous works. The vertical ionization potential I-k’ and each core-electron binding energy (CEBE) were calculated by restricted generalized diffuse ionization (rGDI) and unrestricted generalized transition-state (uGTS) models, respectively. The theoretical core-electron spectra showed better agreement with the experimental ones of the polymers than those due to Koopmans’ theorem. The difference between the calculated and the experimental CEBEs reflected the reasonable WDs of the polymers. (C) 2000 Elsevier Science B.V. All rights reserved.