Electron density distribution in tetralithium hypodiphosphate hexahydrate, Li4P2O6·6H2O

Tetralithium hypodiphosphate hexahydrate, Li4P2O6·6H2O, forms a highly symmetrical crystal structure, where hypodiphosphate anions have \bar 3m (D3d) symmetry. Analysis of the charge distribution (experimental and theoretically calculated) shows that the charges of the P atoms are lower than in phosphates and phosphonates, whereas the O charges are similar. Values of both ρc and ∇(2)ρc suggest that the P-P bond is a weak covalent one, while the P-O one is polarized covalent, with topological parameters similar to those of P-O bonds in phosphates or phosphonates. Theoretical calculations show that the hypodiphosphate anion is relatively insensitive to its coordination environment; this is brought about by the vicinity of cationic P atoms. The localization and delocalization indices have been computed and discussed.