Synthesis, structure, and properties of NaP₇, a phosphorus-rich polyphosphide

NaP₇ is a phosphorus-rich polyphosphide featuring a helical polyphosphide substructure. It can be prepared from the elements as well as via short way transport using CuI as mineralizer additive. As a potential intermediate compound during the reaction of phosphorus with sodium in sodium ion batteries, we investigated the structural and physical properties of this polyphosphide in detail. X-ray single crystal and powder data were collected and the structure was re-determined. Thermal properties were measured and the electronic structure was calculated using DFT methods. NaP₇ is a semiconductor featuring a bandgap in the visible light region.