A deep ultraviolet transparent birefringent monofluorophosphate: Cd_2.5(NH₄)₂(PO₃F)₃Cl ⋅ 2H₂O

Abstract

Herein, we report a new monoclinic, Cd 2.5 (NH 4 ) 2 (PO 3 F) 3 Cl • 2H 2 O (CNPFC, cadmium ammonium monofluorophosphate chloride dihydrate), featuring a [Cd 3 P 2 O 12 ClF 2 ] ∞ double-layered structure. CNPFC is DUV transparent, exhibits a quite large laser induced damage threshold (1.33 × KDP) and emits a purple fluorescence at 410 nm. On an as-synthesized (100)-single crystal plane, the Δn 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 Δn 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.