Application of the dimensional reduction formalism to Pb9−xBax[Li2(P2O7)2(P4O13)2] (x = 0, 2, 6, 7): a series of phosphates with two types of isolated polyphosphate groups

Abstract

A series of phosphates, Pb_9−xBa_x[Li₂(P₂O₇)₂(P₄O₁₃)₂] (x = 0, 2, 6, 7), have been synthesized by a high temperature solution method and the crystal structures were determined by single crystal X-ray diffraction. They are isostructural and crystallize in the triclinic space group P. It is interesting that there are two kinds of isolated polyphosphate anionic groups coexisting in the crystal structure, which is rare among phosphates. Their structures exhibit zero-dimensional [Li₂(P₂O₇)₂(P₄O₁₃)₂]¹⁸⁻ anionic clusters constructed by the LiO₄, P₂O₇ and P₄O₁₃ groups, which are separated by the Pb²⁺ or Ba²⁺ cations. The structure of Pb₉[Li₂(P₂O₇)₂(P₄O₁₃)₂] could be obtained using Li₂O as a dimensional reduction agent to dismantle Pb₃P₄O₁₃. In addition, the infrared spectra and the UV-Vis-NIR diffuse reflectance spectra, as well as thermal analyses are reported. The first-principles theoretical studies are also carried out to understand the relationship between their electronic structures and linear optical properties.