We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaC, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 100 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, With one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the Substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides
Chiesa, M., Giamello, E., DI VALENTIN, C., Pacchioni, G., Sojka, Z., Van Doorslaer, S. (2005). Nature of the chemical bond between metal atoms and oxide surfaces: New evidences from spin density studies of K atoms on alkaline earth oxides. JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 127(48), 16935-16944 [10.1021/ja0542901].
Nature of the chemical bond between metal atoms and oxide surfaces: New evidences from spin density studies of K atoms on alkaline earth oxides
DI VALENTIN, CRISTIANA;PACCHIONI, GIANFRANCO;
2005
Abstract
We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaC, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 100 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, With one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the Substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides
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