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...

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

Scientific Reports ◽

10.1038/s41598-021-86855-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

El Mostafa Benchafia ◽

Xianqin Wang ◽

Zafar Iqbal ◽

Sufian Abedrabbo

Keyword(s):

Crystal Structure ◽

Energy Density ◽

Ab Initio ◽

High Energy ◽

High Energy Density ◽

Marginal Stability ◽

Phonon Modes ◽

High Energy Density Material ◽

Polymeric Nitrogen ◽

Prediction Approach

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.

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

10.21203/rs.3.rs-137877/v1 ◽

2021 ◽

Author(s):

El Mostafa Benchafia ◽

Xianqin Wang ◽

Zafar Iqbal ◽

Sufian Abedrabbo

Keyword(s):

Crystal Structure ◽

Energy Density ◽

High Energy ◽

High Energy Density ◽

Marginal Stability ◽

Phonon Modes ◽

Starting Point ◽

High Energy Density Material ◽

Polymeric Nitrogen ◽

Prediction Approach

Abstract 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.

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Route to high-energy density polymeric nitrogen t-N via He−N compounds

Nature Communications ◽

10.1038/s41467-018-03200-4 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 66

Author(s):

Yinwei Li ◽

Xiaolei Feng ◽

Hanyu Liu ◽

Jian Hao ◽

Simon A. T. Redfern ◽

...

Keyword(s):

Energy Density ◽

High Energy ◽

High Energy Density ◽

Polymeric Nitrogen ◽

N Compounds

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High-pressure new phase of AgN3

Modern Physics Letters B ◽

10.1142/s0217984921503863 ◽

2021 ◽

pp. 2150386

Author(s):

Shifeng Niu ◽

Ran Liu ◽

Xuhan Shi ◽

Zhen Yao ◽

Bingbing Liu ◽

...

Keyword(s):

High Pressure ◽

Energy Density ◽

Density Functional ◽

High Energy ◽

High Energy Density ◽

Detonation Properties ◽

Ambient Conditions ◽

Structure Search ◽

Enthalpy Difference ◽

High Energy Density Material

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.

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