Fig. 5: The effects of polyanion rotation/reorientation on cation diffusion in NaTaCl6 and NaNbCl6.
From: A sodium superionic chloride electrolyte driven by paddle wheel mechanism for solid state batteries
a, b Atomic trajectories from AIMD simulation at 600 K between 13 and 14 ps for (a) NaTaCl6 and (b) NaNbCl6. The trajectories of the six Cl ligands of [TaCl6]/[NbCl6] polyanions are shown in small spheres with different colors (yellow, red, purple, blue, green and brown) in the left panels, while the trajectories of nearby Na atoms are denoted by large pink spheres in the right panels. Coupled motion between the cations and anions are indicated by the arrows: green arrows illustrate the rotational motion of the Cl atoms, and pink arrows indicate the diffusion of Na+-ions (right panels). c The projection of the Ta12-Cl76 bond to the z axis between 13 and 14 ps in NaTaCl6. d The coordinates of Na6 atom during 13-14 ps in NaTaCl6. e The area of the trigonal bottleneck for Na+-ions transport in both NaTaCl6 and NaNbCl6. A widening of the bottleneck size is evidenced when the shared Cl atom rotates in NaTaCl6. f, g The 2D probability density distribution \({\rho }_{{\gamma },r}^{2{\mbox{D}}}\) from AIMD simulations of the Ta(Nb)-Cl-Na angles (γ) and the distance (r) between Cl ligands and Na for (f) NaTaCl6 and (g) NaNbCl6. The color scales at the top right indicate the corresponding probability density values. Pronounced correlation is observed for NaTaCl6, but not for NaNbCl6. h Residence time correlation function for Na+-ions nearest to the polyanion, <hh(t)>, for NaTaCl6 and NaNbCl6. The <PlPl(t)> orientational correlation function is also shown, along with <hPlh(t)Pl(t)> joint time correlation function restricted to Na+-cations nearest to the polyanion. Source data for figure are provided as a Source Data file.
