Intermediate-range chemical ordering of cations in molten RbCl-AgCl

Structural and electronic features of binary Li₂S-P₂S₅ glasses

The atomic and electronic structures of binary Li₂S-P₂S₅ glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PS_x polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li₂S-33P₂S₅, 70Li₂S-30P₂S₅, and 75Li₂S-25P₂S₅ glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PS_x and LiS_y polyhedra increases at a high Li₂S content, and the free volume around PS_x polyhedra decreases. It is conjectured that Li⁺ ions around the face of PS_x polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P₂S₇ anions. The P₂S₇ anions of the weak electrostatic repulsion would causes it to more strongly attract Li⁺ ions than the PS₄ and P₂S₆ anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PS_x and LiS_y polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes.