Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 16: Heterogeneous Catalysis: Theory
O 16.12: Vortrag
Montag, 12. März 2018, 18:00–18:15, MA 141
Atomic and Electronic Structure of Alkali-Doped Zeolites from First Principles — •Debalaya Sarker, Sergey V. Levchenko, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin 14195, Germany
Zeolites posses a crystalline nanoporous aluminosilicate framework with tunable composition, making them ideal candidates for catalytic applications. The substitution of [SiO4] tetrahedra by negatively charged [AlO4]− requires inclusion of counterions. In addition, zeolites readily accommodate dopants, in particular alkali metals [1]. The distribution and concentration of dopants and counterions determine solvated electron density distribution and the electrostatic field inside the zeolitic pores, which have a strong influence on sorbed molecules. We study pristine and M-doped MX and MY zeolites (M = Na, K, Cs), using density-functional theory with a semi-local (PBE) and a hybrid (HSE06) functional with an ab initio van der Waals correction [2]. For different species of the alkali metals, the positions of the counterions in undoped zeolites are found to vary, contrary to the commonly assumed particular cation sites in FAU-type zeolites [3]. Also, the position of counterions with respect to the six-membered ring is found to correlate with electronegativity of the M atom. We found that the distribution of solvated electrons inside the pores is strongly affected by the dopant type and location.
[1] L. R. M. Martens et al., Nature 315, 568 (1985)
[2] A. Tkatchenko and M. Scheffler, PRL 102, 73005 (2009)
[3] D. H. Olson, Zeolites 15, 439 (1995)