Closed and open-shell atomic oxygen on silver: Two distinct patterns of the O 1s binding energy and X-ray absorption O K-edge spectra as revealed by density functional theoryстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The electronic structure of atomic oxygen adsorbed species is studied by means of the density functional theory in the context of the ethylene epoxidation on the silver surface. The adsorbed oxygen species are modeled by the Ag 2O molecule either in its closed ( 1A 1) or open-shell states ( 3B 1 and 1B 1). In both open-shell states the Is level appears to be lower than that in 1A 1 by about 2 eV. This is apparently a sequence of the separation of electron pair, occupying the π*-type highest occupied molecular orbital (HOMO), decreasing the electron density at the oxygen center. Such variation of the O 1s level for closed and open-shell Ag 2O states seems to explain the X-ray photoelectron spectroscopy (XPS) data concerning two distinct atomic oxygen species on silver surface having the O 1s binding energy of about 528 and 530 eV, called nucleophilic and electrophilic oxygen, respectively. The X-ray absorption O K-edge spectra (XANES) calculated for two types of the Ag 2O states by means of multiple-scattered-Xα-based approach appears to be in a qualitative agreement with those experimentally recorded for nucleophilic and electrophilic oxygen.