NaP7–xAsx, Tuning of Electronic Properties in a Polypnictide and Heading towards Helical One-dimensional Semiconductors

Structural, electronic, and vibrational spectroscopic investigations were performed for the solid solution NaP7–xAsx up to x = 3.5 featuring a helical polypnictide substructure. Depending on the As content the LiP7 (for x = 0 to 0.8 and 2.5 to 3.5) or KP15 (x = 1.0 to 2.4) structure type is realized up to an maximum As content of x = 3.5. The crystal structures of two selected phases were determined and the distribution of As in the polyanionic substructure was determined. The full solid solution up to x = 7 was subject to a quantum chemical DFT analysis in order to get insights into the stabilities and phase formation tendencies. Van der Waals interactions between the structure subunits were estimated and first principle investigations towards a delamination and nano structuring of NaP7–xAsx crystals into one-dimensional semiconductors were performed.