All structure optimisations were carried out using the tetragonal unit cell of AST-type zeolites (a ≈ 9 Å, c ≈ 14 Å). The atomic positions and unit cell parameters were optimised, fixing the unit cell to a tetragonal metric (a = b, α = β = γ = 90°), and using the following convergence criteria: maximal geometry change (step size) = 2×10 -5 bohr, maximal residual force (gradient) = 10 -6 Ha bohr -1 , and maximal pressure deviation = 0.01 GPa. The AIMD simulations, which started from the optimised structures, employed a 2×2×1 supercell. These simulations were performed in the canonical (NVT) ensemble for temperatures of 150 K, 298 K, and 573 K, using a Nosé-Hoover thermostat with a timestep of 0.5 fs and a time constant of 50 fs. Three independent AIMD simulations covering 10 ps (20,000 steps) were run for each system at each temperature. The first 2.5 ps (5,000 steps) from each trajectory were discarded (equilibration phase), and the remaining 7.5 ps (15,000 steps) were used in the analysis (production phase). The analysis made use of the VMD code, version 1.9.3, to calculate radial distribution functions (RDFs) for selected combinations of elements, root mean square displacements (RMSDs), and average structures (= average atomic positions over the whole 7. sations in this article were prepared using VESTA.