Crystal structure of the cyclotetraphosphate Ca2[P4O12] · 4 H2O

Ca₂P₄O₁₂] · 4 H₂O crystallizes in the monoclinic space group P2₁/n, a = 7.668, b = 12.895, c = 7.144 Å, β 107.00°, D_x = 2.28 g · cm^?3, Z = 2. In the structure there are ringlike anions, which are composed of 4 PO₄ tetrahedra connected by oxygen bridges. The Ca²⁺ are surrounded by 7 oxygen atoms. Each two cation polyhedra are connected by a common edge to pairs which are isolated from one another. The water molecules form hydrogen bridges with one another and with the anion rings.