Dynamics of small cations in condensed matter systems from combined molecular dynamics and Monte Carlo simulations

• Applicant: Professor Dr. Daniel Sebastiani
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation ; Theoretical Chemistry: Molecules, Materials, Surfaces
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 435886714

The goal of this project is the simulation of the dynamics of small ions in condensed phases, specifically in systems that are relevant for the sector of chemical energy conversion and energy storage. The dynamics of such small ions is fundamentally determined by very fast and very local processes, i.e. the motion of the ions over distances of few Angstrom during few picoseconds. However, experimentally interesting is mainly the other end of both length- and time scales, i.e. micrometers and milliseconds. The idea of the present project is to describe the short local elementary transport processes from quantum chemical simulations, and to feed the resulting data into a stochastic model that allows the modeling of much larger systems on much larger timescales. This concept was very successful for the dynamics of protons during the first funding phase of this project. In the second funding phase, we will extend this concept to two new classes of systems: the dynamics of hydroxide ions (OH-) in aqueous solution (in view of applications in the field of alkaline electrolysis) and the dynamics of lithium ions (Li+) in lithium silicides (Li-Si compounds of varying stochiometry). In both cases, the elementary transport processes will be simulated quantum-chemically (via first-principles molecular dynamics simulations), and subsequently prepared for use in the stochastic model. The application goal of the simulation of the hydroxide ions is the modeling of OH- dynamics in realistic solutions with large structural perturbations such as nanoscale gas bubbles; the application goal of the lithium dynamics simulations is the modeling of the structural evolution of such nanoscale lithium silicides during charge/discharge cycles, which yield considerable volume changes.

• DFG Programme: Research Grants