6Li{31P} rotational-echo, double-resonance studies of lithium ion site dynamics in Li3V2(PO4)3

Low-temperature Li-6{P-31} rotational-echo, double-resonance (REDOR) measurements were used to study lithium mobility within each of the three Li sites in monoclinic Li3V2(PO4)(3). Each of the Li ions was found to experience a different reduced dipolar coupling with the nearest P-31 nucleus. Under fast magic-angle spinning (MAS) conditions (40 kHz), the three crystallographic P-31 sites in Li3V2(PO4)(3) were resolved. On the basis of the known Li-P internuclear distances, the P-31 resonances were assigned by determining the degree of signal attenuation at each phosphorous site. The attenuation of the Li-P dipolar coupling, compared to simulations of the static case, was associated with rattling of the Li ions within the lattice. The relative mobility at each Li site is correlated with structural properties including the shortest Li-O contact within the void and bond valence calculations.