Stabilization of Polynitrogen Anions in Tantalum–Nitrogen Compounds at High Pressure

Abstract

The synthesis of polynitrogen compounds is of great importance due to their potential as high-energy-density materials (HEDM), but because of the intrinsic instability of these compounds,t heir synthesis and stabilization is af undamental challenge.P olymeric nitrogen units whichm ay be stabilized in compounds with metals at high pressure are now restricted to non-branched chains with an average NÀNb ond order of 1.25, limiting their HEDM performances.Herein, we demonstrate the synthesis of an ovel polynitrogen compound TaN 5 via ad irect reaction between tantalum and nitrogen in adiamond anvil cell at circa 100 GPa. TaN 5 is the first example of am aterial containing branched all-single-bonded nitrogen chains [N 5 5À ] 1 .A part from that we discover two novel TaN compounds:T aN 4 with finite N 4 4À chains and the incommensurately modulated compound TaN 2Àx ,which is recoverable at ambient conditions.

Stabilization of pentazolate anions in the high-pressure compounds Na2N5and NaN5and in the sodium pentazolate framework NaN5·N2

“…This inhomogeneity, typical for high-pressure DAC experiments, makes the synthesis of phase-pure samples challenging, but at the same time allows to probe wide compositional interval in one experiment. [22][23][24][25][26] In this study we combined high-resolution Raman mapping with X-ray diffraction analysis to spatially resolve various phases of the laser-heated sample. Fig.…”

Stabilization of Polynitrogen Anions in Tantalum–Nitrogen Compounds at High Pressure

“…Theh eating of Ta metal with nitrogen in aD AC at around 100 GPa and 2200(200) Kresulted in the formation of two novel nitrogen-rich compounds TaN 4 and TaN 5 as determined from the single-crystal XRD analysis. [38] TaN 5 has an orthorhombic space group Fdd2(No.43) with 1T aand 5Npositions occupying Wyckoff sites 16b. Nitrogen atoms form unprecedented branched chains infinitely expanding along the c-axis (Figure 1a,b ] 1 anion agrees with the common oxidation state of Ta V and should have the Lewis formula shown in Figure 1c.…”

Anionic N18 Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN6 and Y2N11 at 100 GPa

“…Whereas a significant number of studies on binary metal‐nitrogen compounds of alkali, alkaline earth, and transition metal elements under high pressure have been conducted, [1–7, 9–29] the high‐pressure chemistry and physical properties of rare earth metal nitrides are almost unknown. Until recently, in the yttrium‐nitrogen system, only one binary Y−N compound was known: cubic yttrium nitride YN with the rock salt structure [39] .…”