τ and l were optimized using bulk β-Li 3 PS 4 and 75Li units in bulk β-Li 3 PS 4 , depicted in Fig. (a), exhibit a small distribution around the vertices of a tetrahedron due to restricted rotational motion. In contrast, the random rotational motion of PS 4 3units in all directions spreads the S trajectories over the entire spherical surface, as shown in Fig. ). These visually recognizable differences in trajectories are quantitatively evaluated using the q l parameter defined in Eq. ( ).