Nonequilibrium molecular dynamics for accelerated computation of ion-ion correlated conductivity beyond Nernst-Einstein limitation

Condensed matters with high ionic conductivities are crucial in various solid devices such as solid-state batteries. The conduction is characterized by the cooperative ionic motion associated with the high carrier density. However, the high cost of computing correlated ionic conductivities has forced almost all ab initio molecular dynamics (MD) to rely on the Nernst-Einstein dilute-solution approximation, which ignores the cross-correlation effect. Here we develop a chemical color-diffusion nonequilibrium MD (CCD-NEMD) method, which enables to calculate the correlated conductivities with fewer sampling steps than the conventional MD. This CCD-NEMD is demonstrated to well evaluate the conductivities in the representative solid electrolyte bulk Li10GeP2S12 and Li7La3Zr2O12. We also applied CCD-NEMD to the grain boundary of Li7La3Zr2O12 and demonstrated its applicability for calculating interfacial local conductivities, which is essential for investigating grain boundaries and composite electrolytes. CCD-NEMD can provide further accurate understanding of ionics with ionic correlations and promote developing solid devices.

Automated summary

Condensed matters with high ionic conductivities are essential in solid-state devices. However, computing correlated ionic conductivities is costly, leading to the use of approximations. This study presents a new method, CCD-NEMD, which allows for the calculation of correlated conductivities with fewer sampling steps. It is demonstrated to be effective in evaluating conductivities in solid electrolytes and can be applied to investigate grain boundaries and composite electrolytes.