Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 92: Electronic Structure Theory
O 92.2: Vortrag
Freitag, 5. April 2019, 10:45–11:00, H5
First-Principles Study of Cation Distribution and Elec- tron Solvation in Alkali-Metal Doped Zeolites — •Debalaya Sarker1, Matthias Scheffler1, and Sergey V Levchenko1,2,3 — 1Fritz-Haber-Institut der MPG, Berlin, DE — 2Skolkovo Innovation Center, Moscow, RU — 3NUST MISIS, Moscow, RU
Zeolites are nanoporous aluminosilicates with extraframework cations M+, M=Na, K, Cs. Additional doping of M results in M clusters inside the zeolite pores [1], making them potential basic catalysts. Despite extensive experimental efforts, the size, charge state, and stability of the clusters, and in particular how the electrons provided by the M dopants are distributed (solvated) are still debated. By varying the Si:Al ratio, M type, and doping amount, we have studied the M distributions and electron solvation in faujasite-zeolites using van der Waals corrected [2] DFT with semilocal (PBE) and hybrid (HSE06) functionals. A cluster-expansion model is trained to explore the configurational space of the M distribution at finite temperatures. We find that the amount of exact exchange α in HSE06 has no effect on geometry and relative energies. At Si:Al≈2.4, for all α the solvated electrons are localized within ∼3 Å around the M43+ clusters formed inside smaller β cages, but for Si:Al=5 and α 0.1 delocalization over the unit cell occurs. Moreover, the equilibrium distribution of framework Al is found to be different for K- and Na-exchanged zeolites, affecting the M clustering in the zeolitic pores.
[1] J. A. Rabo et al., Discuss. Faraday Soc. 41, 328 (1966).
[2] A. Tkatchenko, M. Scheffler, Phys. Rev. Lett. 102, 73005 (2009).