Finally, from Na2V2(PO4)3 to Na1V2(PO4)3, the structure is back to rhombohedral unit cell (R3c), having the Na(2) site fully emptied. It is interesting that from Na4V2(PO4)3 to Na2V2(PO4)3, the Na(2b) position tends to be more occupied than the Na(2a) positions. This may be related to different connectivities of Na(2a) and Na(2b) with the Na(1) site.