Toward Realistic Transfer Rates within the Coupled Molecular Dynamics/Lattice Monte Carlo Approach

We refine our recently developed coupled molecular dynamics/lattice Monte Carlo (cMD/LMC) scheme for the simulation of protonation dynamics in complex hydrogen-bonded solids in view of improving the resulting transport processes. The distance dependency of the proton jump rate between lattice sites and its dependence on additional geometric criteria (bond angles) are derived in a systematic and consistent way. The distance dependency follows an accurate potential energy surface (PES) scan from quantum chemical calculations. The novel geometric criterion takes into account that proton hopping occurs almost exclusively along linear hydrogen bonds. We illustrate the capabilities and the versatility of our scheme on the example of two chemically quite different condensed phase systems: a crystalline solid acid compound and a liquid crystal. Surprisingly, we find that our cMD/LMC scheme yields converged mobility parameters even when based on underlying ab initio molecular dynamics (AIMD) trajectories which themselves are not fully converged. Our method yields more accurate values for the mean square displacement, the OH bond autocorrelation function and the proton jump frequencies in agreement with both reference AIMD simulations and experimental values.