Structure of Intercalated Cs in Zeolite ITQ-4: An Array of Metal Ions and Correlated Electrons Confined in a Pseudo-1D Nanoporous Host

The presence of ${\mathrm{C}\mathrm{s}}^{+}$ ions in the pseudo-1D nanopores of zeolite ITQ-4, ${\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$, is confirmed by x-ray diffraction and atomic pair distribution function analysis. Inside the nanopores the ${\mathrm{C}\mathrm{s}}^{+}$ ions are found to assemble in zigzag chains and thus form an extended, positively charged sublattice providing charge balance for a low-density electron gas also confined to the nanopores.

Figure 1

Powder diffraction patterns (a) and the corresponding structure functions (b) of pristine ${\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$ and electrides ${\mathrm{C}\mathrm{s}}_x{\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$. A portion of the diffraction patterns is given on an expanded scale in the inset.

Figure 2

Experimental (circles) and model (line) PDFs for ${\mathrm{C}\mathrm{s}}_x{\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$ ($x=0,3.6,4.6$).

Figure 3

Cs differential PDFs for ${\mathrm{C}\mathrm{s}}_x{\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$ electrides. Experimental data (circles) and model data (line).

Figure 4

Fragment of the atomic structure of ${\mathrm{C}\mathrm{s}}_x{\mathrm{S}\mathrm{i}}_{32}{\mathrm{O}}_{64}$ with ${\mathrm{C}\mathrm{s}}^{+}$ ions (red circles) in the nanopores assembled in zigzag chains. Oxygen atoms are in blue and silicon is in black.