Volume 60, Issue 16 pp. 9003-9008
Research Article

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

Dr. Maxim Bykov

Corresponding Author

Dr. Maxim Bykov

Department of Mathematics, Howard University, Washington, DC, 20059 USA

The Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, 20015 USA

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Dr. Elena Bykova

Dr. Elena Bykova

The Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, 20015 USA

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Dr. Alena V. Ponomareva

Dr. Alena V. Ponomareva

Materials Modeling and Development Laboratory, National University of Science and Technology 'MISIS', 119049 Moscow, Russia

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Prof. Dr. Igor A. Abrikosov

Prof. Dr. Igor A. Abrikosov

Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183 Linköping, Sweden

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Dr. Stella Chariton

Dr. Stella Chariton

Center for Advanced Radiation Sources, University of Chicago, Lemont, IL, 60437 USA

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Dr. Vitali B. Prakapenka

Dr. Vitali B. Prakapenka

Center for Advanced Radiation Sources, University of Chicago, Lemont, IL, 60437 USA

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Prof. Dr. Mohammad F. Mahmood

Prof. Dr. Mohammad F. Mahmood

Department of Mathematics, Howard University, Washington, DC, 20059 USA

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Prof. Dr. Leonid Dubrovinsky

Prof. Dr. Leonid Dubrovinsky

Bayerisches Geoinstitut, 95447 Bayreuth, Germany

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Dr. Alexander F. Goncharov

Dr. Alexander F. Goncharov

The Earth and Planets Laboratory, Carnegie Institution for Science, Washington, DC, 20015 USA

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First published: 08 February 2021
Citations: 55

Graphical Abstract

Direct reaction between nitrogen and tantalum at approximately 100 GPa results in the energetic nitrogen-rich compounds TaN4 and TaN5, which feature N4 chains and unprecedented branched single-bonded polymeric nitrogen chains in the crystal structures, respectively. TaN5 possesses an extraordinary volumetric energy density of 18 kJ cm−3, exceeding well-known high-energy-density materials.

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, their synthesis and stabilization is a fundamental challenge. Polymeric nitrogen units which may be stabilized in compounds with metals at high pressure are now restricted to non-branched chains with an average N−N bond order of 1.25, limiting their HEDM performances. Herein, we demonstrate the synthesis of a novel polynitrogen compound TaN5 via a direct reaction between tantalum and nitrogen in a diamond anvil cell at circa 100 GPa. TaN5 is the first example of a material containing branched all-single-bonded nitrogen chains [N55−]. Apart from that we discover two novel Ta–N compounds: TaN4 with finite N44− chains and the incommensurately modulated compound TaN2−x, which is recoverable at ambient conditions.

Conflict of interest

The authors declare no conflict of interest.

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