Chemical preparation, single-crystal X-ray structure, and infrared and polarized Raman spectra of a new cadmium dibarium bis(monohydrogen monophosphate) bis(dihydrogen monophosphate) are presented. The atomic arrangement consists of anionic layers formed by HPO 2 Ψ 4 and H2PO Ψ 4 groups connected to each other through strong hydrogen bonds, resulting in a two-dimensional network. These sheets are held together by six oxygencoordinated Cd 2 Ψ and nine oxygen-coordinated Ba 2 Ψ ions to build a three-dimensional framework. An assignment of lattice and internal vibrations in terms of symmetry species and approximate type of motion is given. A comparison with the vibrational fundamentals of the PO 3Ψ 4 ion in the isostructural CaBa2(HPO4)2(H2PO4)2 (CaBa2) is also discussed. Band positions are found to be largely independent of the positive ion. Crystal data for CdBa2(HPO4)2(H2PO4)2 (CdBa2): M β«Ψβ¬ 773.08 g mol Ψ 1 , monoclinic, space group P21/c (No. 14), a β«Ψβ¬ 5.434(4) A > , b β«Ψβ¬ 10.140(2) A > , c β«Ψβ¬ 12.298(2) A > , β«Ψβ¬ 100.43(3)3, Z β«Ψβ¬ 2, R1/wR2 β«Ψβ¬ 0.024/0.066 [1858 observed re6ections with I'6 (I)].