Ab Initio Molecular Dynamics Study of the Superacid System SbF_5/HF Solution

摘要

We have investigated one of the strongest superacid systems, SbF_5 in liquid HF, by ab initio molecular dynamics simulation. In dilute solution a barrierless, diffusion-limited fluorination reaction takes place ot form the SbF_6~- anion and H_2F~+ cation. The initial contact ion pair evolves to become a fully separation ion pair by a series of stepwise, incoherent proton jumps. On average, the SbF_6~- anion had an octahedral structure with the average bond length of 1.9A. The cationic species is a protonated HF chain, which mediates the fast proton jump process.