Synthesis, Structure, and Properties of NaP 7, a Phosphorus-rich Polyphosphide. -NaP 7 is prepared from stoichiometric quantities of red phosphorus and Na in the presence of purified CuI as mineralizer (evacuated graphitized silica tubes, 823 K, 7 d). The compound crystallizes in the tetragonal space group I4 1/acd with Z = 16 (single crystal XRD). The structure consists of  1 ] helical tubes running along the c axis. The compound decomposes peritectically into white phosphorus, Na 3P11, and Na3P7. DFT calculations show that NaP 7 is a semiconductor featuring an optical bandgap of 1.71-1.82 eV in the visible light region. -(GROTZ, C.; KOEPF, M.; BAUMGARTNER, M.; JANTKE, L.-A.; RAUDASCHL-SIEBER, G.; FAESSLER, T. F.; NILGES*, T.; Z. Anorg. Allg. Chem. 641 (2015) 8-9, 1395-1399, http://dx.