Pressure-Stabilized High-Energy-Density Material YN10

Polynitrogen compounds have been intensively studied for potential applications as high energy density materials, especially in energy and military fields. Here, using the swarm intelligence algorithm in combination with first-principles calculations, we systematically explored the variable stoichiometries of yttrium–nitrogen compounds on the nitrogen-rich regime at high pressure, where a new stable phase of YN10 adopting I4/m symmetry was discovered at the pressure of 35 GPa and showed metallic character from the analysis of electronic properties. In YN10, all the nitrogen atoms were sp2-hybridized in the form of N5 ring. Furthermore, the gravimetric and volumetric energy densities were estimated to be 3.05 kJ/g and 9.27 kJ/cm-1 respectively. Particularly, the calculated detonation velocity and pressure of YN10 (12.0 km/s, 82.7 GPa) was higher than that of TNT (6.9 km/s, 19.0 GPa) and HMX (9.1 km/s, 39.3 GPa), making it a potential candidate as a high-energy-density material.

High-pressure new phase of AgN3

The structural evolutionary behaviors of AgN3 have been studied by using the particle swarm optimization structure search method combined with the density functional theory. One stable high-pressure metal polymeric phase with the [Formula: see text] space group is suggested. The enthalpy difference analysis indicates that the Ibam-AgN3 phase will transfer to the I4/mcm-AgN3 phase at 4.7 GPa and then to the [Formula: see text]-AgN3 phase at 24 GPa. The [Formula: see text]-AgN3 structure is composed of armchair–antiarmchair N-chain, in which all the N atoms are sp2 hybridization. The inherent stability of the armchair–antiarmchair chain and the anion–cation interaction between the N-chain and Ag atom induce a high stability of the [Formula: see text]-AgN3 phase, which can be captured at ambient conditions and hold its stable structure up to 1400 K. The exhibited high energy density (1.88 KJ/g) and prominent detonation properties ([Formula: see text] Km/s; [Formula: see text] GPa) of the [Formula: see text]-AgN3 phase make it a potentially high energy density material.

Predicting the crystal structure of $$\hbox {N}_5\hbox {AsF}_6$$ high energy density material using ab initio evolutionary algorithms

Abstract$$\hbox {N}_5\hbox {AsF}_6$$ N 5 AsF 6 is the first successfully synthesized salt that has a polymeric nitrogen moeity ($$\hbox {N}_5^+$$ N 5 + ). Although 12 other $$\hbox {N}_5^+$$ N 5 + salts followed, with $$\hbox {N}_5\hbox {SbF}_6$$ N 5 SbF 6 and $$\hbox {N}_5\hbox {Sb}_2\hbox {F}_{11}$$ N 5 Sb 2 F 11 being the most stable, the crystal structure of $$\hbox {N}_5\hbox {AsF}_6$$ N 5 AsF 6 remains unknown. Currently, it is impossible to experimentally determine the structures of $$\hbox {N}_5\hbox {AsF}_6$$ N 5 AsF 6 due to its marginal stability and explosive nature. Here, following an ab initio evolutionary prediction and using only the stoichiometry of $$\hbox {N}_5\hbox {AsF}_6$$ N 5 AsF 6 as a starting point, we were able to reveal the crystal structure of this high energy density material (HEDM). The $$\hbox {C}_{2V}$$ C 2 V symmetry of the $$\hbox {N}_5^+$$ N 5 + cation, as suggested from earlier investigations, is confirmed to be the symmetry adopted by this polymeric nitrogen within the crystal. This result gave full confidence in the validity of this crystal prediction approach. While stability of the $$\hbox {N}_5^+$$ N 5 + within the crystal is found to be driven by electronic considerations, the marginal stability of this HEDM is found to be related to a partial softening of its phonon modes.

Crystal structure of 3-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole

The crystal structure of a novel high-energy density material 3-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole C5HN9O8 was determined and refined using laboratory powder diffraction data. The diffraction data and database analysis were insufficient to distinguish two candidate structures from the solution step. Density functional theory with periodic boundary conditions optimizations were used to choose the correct one. 3-[(3,4-Dinitro1H-pyrazol-1-yl)-NNO-azoxy]-4-nitro-1,2,5-oxadiazole crystallizes in space group Pbca with a = 8.3104(2) Å, b = 14.2198(5) Å, c = 19.4264(7) Å, V = 2295.66(14) Å3. The molecular conformation contains a weak intramolecular hydrogen bond C–H⋯O–N, and the structure is dominated by weak O⋯π and O⋯O contacts.

Crystal structure of 3,3′-(E)-diazene-1,2-diylbis{4-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-1,2,5-oxadiazole}

The crystal structure of a novel high-energy density material 3,3′-(E)diazene-1,2-diylbis{4-[(3,4-dinitro-1H-pyrazol-1-yl)-NNO-azoxy]-1,2,5-oxadiazole} (C10H2N18O12) was determined and refined using laboratory powder diffraction data. The title compound crystallizes in space group P21/c with a = 9.5089(3) Å, b = 11.6331(4) Å, c = 10.6270(3) Å, β = 116.2370(12), V = 1054.43(6) Å3. The asymmetric unit contains half of the molecule. The molecular conformation contains a weak intramolecular hydrogen bond C–H⋯O–N, both nitro groups are disordered, and the structure is dominated by weak O⋯π and O⋯O contacts.

Predicting High Energy Density Materials using Abinitio Evolutionary Algorithms: The Results for N5AsF6

N5AsF6 is the first successfully synthesized salt that has a polymeric nitrogen moeity (N5+). Although 12 other N5+ salts followed, with N5SbF6 and N5Sb2F11 being the most stable, the crystal structure of N5AsF6 remains unknown. Currently, it is impossible to experimentally determine the structures of N5AsF6 due to its marginal stability and explosive nature. Here, following an ab initio evolutionary prediction and using only the stoichiometry of N5AsF6 as a starting point, we were able to reveal the crystal structure of this high energy density material (HEDM). The C2V symmetry of the N5+ cation, as suggested from earlier investigations, is confirmed to be the symmetry adopted by this polymeric nitrogen within the crystal. This result gave full confidence in the validity of this crystal prediction approach. While stability of the N5+ within the crystal is found to be driven by electronic considerations, the marginal stability of this HEDM is found to be related to a partial softening of its phonon modes.

Conduction transition and electronic conductivity enhancement of cesium azide by pressure-directed grain boundary engineering

Alkali metal azides have attracted considerable experimental and theoretical efforts as they are the promising starting materials for the synthesis of polymeric nitrogen, a high-energy-density material. This work reports the...

Pressure-stabilized GdN6 with armchair-antiarmchair structure as a high energy density material

The quest for high-energy-density materials is an active research field in materials science and industrial applications. Using the swarm-intelligence structure search method and first-principles calculations, we identify several hitherto unknown...