Dynamics Study of Superionic Conducting Glass Na3PS4 Using Quasi‐Elastic Gamma‐Ray Scattering: Analysis Based on Diffraction and Reverse Monte Carlo–Density Functional Theory Modeling

Abstract

Superionic conducting glass Na3PS4 has been studied as a candidate of electrolyte for all‐solid‐state batteries. However, the microscopic dynamics of relaxation units, Na and PS4 ions, in Na3PS4 glass is not known despite its essential importance to the ionic conduction mechanism. Momentum‐transfer dependence data of the experimental intermediate scattering function values for Na3PS4 glass is measured at subpicosecond and nanosecond time scales, respectively, by a quasi‐elastic gamma‐ray scattering experiment using time‐domain interferometry. The dynamics data is analyzed based on Faber–Ziman partial static structure factors that are obtained using a model glass structure constructed from the combination of density functional theory calculation and reverse Monte Carlo modeling for diffraction spectra. The analysis successfully explains the experimental result and reveals the vibrational and angstrom‐scale translational motion of respective relaxation units, i.e., Na and PS4 ions in the unique time scales: the translational motion of some Na ions occurs at picosecond to nanosecond time scale, whereas the movement of PS4 ions rarely occurs in the superionic conducting Na3PS4 glass.