To understand the exceptional separation performance of Li-2-SAPO-RHO, the diffusion behaviour of C2H4 and C2H6 through d8rs connecting adjacent lta cavities in SAPO-RHO was investigated using ab initio molecular dynamics (AIMD) simulations with enhanced sampling same 8MR (2Si-1Li-8MR-1H-8MR; fig. ). The relative stability of these structures (table ) is consistent with the Li + and D + distribution derived from the refined NPD data (fig. and).