Li12 P3 N9 was synthesized by solid-state reaction of Li3 N and P3 N5 at 790 °C. It is made up of non-condensed [P3 N9 ]12- dreier-rings of PN4 -tetrahedra. The corresponding high-pressure polymorph, Li4 PN3 , was synthesized under high-pressure/high-temperature conditions from Li12 P3 N9 or LiPN2 and Li7 PN4 at 6 or 7 GPa, respectively, using the multianvil technique. Li4 PN3 is the first lithium catena-nitridophosphate and contains PN3 zweier-chains of corner sharing PN4 -tetrahedra. To confirm the structure elucidated from single-crystal X-ray data, Rietveld refinement, 6 Li, 7 Li, and 31 P solid-state NMR spectroscopy, FTIR spectroscopy and EDX measurements were carried out. To examine the phase transition of Li12 P3 N9 to Li4 PN3 at 6 GPa and to corroborate the latter as the corresponding high-pressure polymorph, DFT calculations were conducted. Electronic band gap and electron localization function (ELF) calculations were carried out to elucidate the electronic properties and bonding behavior of both polymorphs.
Keywords: density functional calculations; high-pressure chemistry; high-temperature chemistry; nitrides; solid-state structures.
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