Understanding H-ion transport dynamics in superionic conductor BaH₂

Superionic conductors have received increasingly attentions due to the potential applications to energy storage, fuel cells, solid electrolytes, etc. BaH₂ was experimentally reported as a superionic conductor which exhibits ionic conductivity of nearly 0.2 S/cm at 630 °C, an order of magnitude larger than that of state-of-the-art proton-conducting perovskites at this temperature[1]. However, the mechanism of H-ion conduction therein still remains investigations. In this work, we use first-principles nudged elastic band (NEB) simulations to compute the energy barriers. The quantum dynamic effects were considered by path-integral Monte Carlo(PIMC) sampling. Free energy surface was calculated using PIMC combined with umbrella sampling method. Furthermore, kinetic Monte Carlo (kMC) simulations were carried out to compute the ionic mobilities and conductivities which match well with the experimental data.
[1] Verbraeken, Maarten C.,et al. Nature materials 14.1 (2015): 95.