Figure 1.

(a) A 2 × 1 × 1 supercell of the IZA structure framework of PSI (blue = Si and red = O atoms). (b) The isosurface of the potential energy at 60 kJ/mol, which defines the accessible pore volume, shows that PSI has a one-dimensional tunnel system accessible to CH₄. (c) The TSs of the one-dimensional CH₄ diffusion are colored by energy levels (blue = low to red = high). (d) The independent TS surfaces dividing basin pairs are colored differently; the black points show the positions that represent the lattice sites used in the kMC simulation.