Recoverability of N₄^x–Anions to Ambient Pressure: A First-Principles Study ofcyclo- andsyn-Tetranitrogen Units

Abstract

In this paper, we have analyzed the possibility of various neutral and anionic forms of both cyclic and acyclic N4 species to be recovered to ambient conditions using state-of-the-art computational techniques. Phonon dispersion and mechanical properties calculations as well as ab initio molecular dynamics simulations revealed that syn-tetranitrogen units are kinetically stable only in the form of N4 4– anion. Meanwhile, salts of cyclic N4 (c-N4, tetrazete) with alkali, alkaline earth metals, and aluminum appeared to be dramatically stable at ambient conditions for a wide range of oxidation states of c-N4 x– from x = 1–3. Varying both metal and stoichiometry, one can obtain salts with a wide range of properties: band gap (1–5 eV), bulk modulus (36–196 GPa), enthalpy of formation (from −21 to 660 kJ mol–1), and so forth. Thus, crystal structure prediction and comprehensive characterization, which included bonding nature, stability criteria, spectral properties along with thermodynamic and energetic characteristics of c-N4 and its salts (Na2N8, Li2N4, MgN4, and AlN4) as well as calcium salt of syn-N4 4– (Ca2N4) are performed in this work. The obtained results significantly expand our understanding of the possible forms of nitrogen existence in nature, which, if synthesized, can find a number of interesting applications.

Interaction of Nitrogen-Rich Cations with Azotriazolone Anions through Ion Exchange Results in the Formation of Energetically Stable and Insensitive Compounds

“…In the field of high-energy materials science, the intrinsic properties of reactants are considered fundamental characteristics of high-energy materials. However, the calorific value, serving as a crucial technical parameter, holds significant reference value in assessing the performance of high-energy materials. − All salt compounds had a high positive heat of formation (297.8–942.5 kJ mol –1 ), which is significantly higher than that of TNT. According to the calculation of the enthalpy of organic salt formation by the Born–Haber energy cycle, an isobond reaction of anions and cations is first constructed.…”

Structural, Electronic, and Mechanical Properties of Nitrogen Nanotubes: The Effect of Size and Strain

“…The molecular nitrogen allotrope bipentazole (N10) is thermally stable at ambient temperature due to the formation of strongly aromatic pentazole rings . The AIMD simulations revealed that syn-tetra nitrogen units are kinetically stable only in the form of N 4 4– anion whereas syn- N 4 2– anions are not stable at ambient pressure. Due to their low thermal stability, aryl pentazoles convert into cyclo-pentazolate salts by cleaving the C–N bond and the pentazoles are thermally stable up to 77 °C …”

Lanthanium nitride LaN9 featuring azide units: the first metal nine-nitride as a high-energy-density material

“…Metal atoms play a key role in stabilizing nitrogen-bearing polyanions through charge transfer mechanisms at high pressures. Extensive theoretical and experimental investigations have demonstrated that the majority of metals spanning the periodic table, including alkali metals, [10][11][12][13][14][15][16][17][18][19] alkaline-earth metals, [20][21][22][23][24] transition metals, [25][26][27][28][29][30] and rare-earth metals, [31][32][33][34] are capable of engaging in reactions with nitrogen atoms at high pressure (please see the ESI †). This capability facilitates the formation of a diverse range of polynitrogen frameworks.…”

“…This capability facilitates the formation of a diverse range of polynitrogen frameworks. Of particular interest are frameworks encompassing a wide array of polynitrogen units, including azides (N 3 À ) as exemplified in alkali metal azides AN 3 (M = Li, Na, K, Rb, or Cs), 10,11,18,[35][36][37] pentazolate (N 5 À ) as observed in MN 5 (M = Li, Na, K, Rb, Cs, Ca, Sr, Ba, Cu, Ta) 15,18,19,[22][23][24][38][39][40] or MN 10 (M = Be, Mg, Ba), 24,41,42 benzene (N 6…”