A Deep Ultraviolet Transparent Birefringent Monofluorophosphate: Cd2.5(NH4)2(PO3F)3Cl ⋅ 2H2O

Herein, we report a new monoclinic, Cd-2.5(NH4)(2)(PO3F)(3)Cl . 2H(2)O (CNPFC, cadmium ammonium monofluorophosphate chloride dihydrate), featuring a [Cd3P2O12ClF2](infinity) double-layered structure. CNPFC is DUV transparent, exhibits a quite large laser induced damage threshold (1.33xKDP) and emits a purple fluorescence at 410 nm. On an as-synthesized (100)-single crystal plane, the Delta n(obv.)(100)=n(c)-n(b)=0.012 is measured at 546 nm, which is consistent with the theoretical calculated 0.017. The birefringence of CNPFC is theoretically calculated to be Delta n(cal.)=n(Z)-n(X)=0.035. We further demonstrate that the diverse coordination environments and inter-unit linkages of the Cd-centered polyhedra as well as different hydrogen bonding interactions give rise to an interesting structural relationship among three related compounds.