Structural and transport properties of α-RbCu₄Cl₃I₂ at room temperature by molecular dynamics simulation

Considering α-RbCu₄Cl₃I₂ is isostructural with α-RbAg₄I₅, in this work, we built a molecular dynamics simulation system of the former superionic conductor with an empirical pairwise potential model, which was verified on the latter crystal, including long-ranging Coulomb, short-ranging Born–Mayer, charge–dipole, and dipole–quadrupole interactions. The corresponding parameters were collected from the crystal structure and several reports of interionic potentials in alkali halides. The coordination number of fixed ions was examined, and the dynamic distribution of dissociative Cu⁺ was described by the radial distribution function. The diffusion behavior of the ions was evaluated with mean square displacements and velocity auto-correlation functions. The diffusion coefficient of copper ions obtained is (47.9 ± 6.1) × 10⁻⁷ cm²/s, which is approximately 37 times that of the simulation result (1.3 ± 0.1) × 10⁻⁷ cm²/s of silver in α-RbAg₄I₅ at room temperature. In this work, the diffusion coefficient of Cu⁺ was first discussed by molecule simulation, while there are few experimental reports.