SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 12: Poster Session I: Electronic structure theory: General
O 12.2: Poster
Montag, 1. März 2021, 10:30–12:30, P
Solvated Electrons in Alkali Metal Doped Zeolites: Insights from Ab-initio Atomistic Thermodynamics — •Debalaya Sarker1,2, Maria Troppenz3, Santiago Rigamonti3, Claudia Draxl3, Sergey V Levchenko1,2, and Matthias Scheffler2 — 1Skoltech, Moscow, RU — 2Fritz-Haber-Institut der MPG, DE — 3Humboldt-Universität zu Berlin, DE
Doping nanoporous aluminosilicate zeolites viz. faujasite Y, with alkali metal atoms (M) is a promising way of producing outstanding catalysts. The dopants, along with extra-framework M atoms, often form M43+, clusters inside zeolite pores, leaving the valence electron of the dopant solvated and available for catalysis. Despite extensive experimental efforts[1], the distribution of the dopants and solvated electrons remains debated to date. Combining a cluster-expansion model, parameterized with density-functional theory calculations, with ab-initio thermodynamics, we address this issue. The electronic structure for low-energy configurations is calculated with the hybrid functional HSE06. We find that even at room temperature, Na atoms in NaY zeolites with 2 extra-framework atoms/unit cell on average redistribute such that areas with lower and higher local concentrations emerge. The redistribution is driven by increased configurational disorder, mainly at higher concentrations. This explains why solvated electrons can be located inside both small and large cages in NaY, reconciling experiments that assign the solvated electrons to a particular pore type.
[1] A. R. Armstrong et al., J. Am. Chem. Soc. 117, 9087 (1995).