  Ion dynamics that drive the transport and thermophysical properties of molten
salts are poorly understood due to challenges in precisely quantifying the
spatial and temporal fluctuations of specific ions in highly disordered
systems. While the Van Hove correlation function (VHF) obtained from inelastic
neutron scattering (INS) probes these dynamics directly, its interpretation is
limited by the inherent species-averaging of experiments, which obscures
analysis of key ion transport and solvation mechanisms. Here, ab initio
molecular dynamics (AIMD) is used to model the VHF, unravel its partial
contributions, and elucidate its underlying ionic transport mechanisms. Slow
decorrelation is revealed for oppositely charged ions (Mg2+ and Cl-) caused by
ion exchange across the solvation shell between adjoining ionocovalent
complexes. Furthermore, transport coefficients are accurately recovered and
connections between macroscopic properties and ion dynamics are revealed. This
study demonstrates the potential of ab initio-informed VHF to resolve
long-standing challenges in uncovering relationships between picosecond-scale
ion dynamics, mechanisms, and emergent physical properties of molten salts.
