For the structure of Na2V2(PO4)3 using the space group P21/c (Model 1), the refined cell ), it appears that the environment of both V(1a) and V(1b) are similar with an average V-O bond distance of 1.99(9) Å, which suggests that V 3+ and V 4+ are randomly distributed over the V(1a) and V(1b) positions. For the Na crystallographic sites, the Na(1) and Na(2) sites split into two Na(1) (labeled Na(1a) and Na(1b)) and three Na(2) positions (labeled Na(2a1), Na(2a2), and Na(2b)) in the space group P21/c. The refined occupancy factor for Na(2a2) position was 0.08 (7), which can be considered as fully empty.