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155 results on '"Mahmood, Mohammad F."'

1. Structural diversity of molecular nitrogen on approach to polymeric states

Author

Goncharov, Alexander F., Batyrev, Iskander G., Bykova, Elena, Brüning, Lukas, Chen, Huawei, Mahmood, Mohammad F., Steele, Andew, Giordano, Nico, Fedotenko, Timofey, and Bykov, Maxim

Subjects
Condensed Matter - Materials Science
Abstract

Nitrogen represents an archetypal example of material exhibiting a pressure driven transformation from molecular to polymeric state. Detailed investigations of such transformations are challenging because of a large kinetic barrier between molecular and polymeric structures, making the transformation largely dependent on kinetic stimuli. In the case of nitrogen, additional complications occur due to the rich polymorphism in the vicinity of the transition. Here, we report the observation of both molecular (\theta) and polymeric (BP) phases, crystallized upon temperature quenching of fluid nitrogen to room temperature at 97-114 GPa. Synchrotron single-crystal X-ray diffraction, Raman spectroscopy, and first-principles theoretical calculations have been used for diagnostics of the phases and determination of their structure and stability. Molecular \theta-nitrogen is the most stable among molecular phases bordering the stability field of polymeric phases, partially settling a previously noted discrepancy between theory and experiment concerning the thermodynamic stability limit of molecular phases., Comment: 23 pages, 11 figures, 3 tables

Published
2023

2. High-pressure synthesis of Dirac materials: layered van der Waals bonded BeN$_4$ polymorph

Author

Bykov, Maxim, Fedotenko, Timofey, Chariton, Stella, Laniel, Dominique, Glazyrin, Konstantin, Hanfland, Michael, Smith, Jesse S., Prakapenka, Vitali B., Mahmood, Mohammad F., Goncharov, Alexander F., Ponomareva, Alena V., Tasnádi, Ferenc, Abrikosov, Alexei I., Masood, Talha Bin, Hotz, Ingrid, Rudenko, Alexander N., Katsnelson, Mikhail I., Dubrovinskaia, Natalia, Dubrovinsky, Leonid, and Abrikosov, Igor A.

Subjects
Condensed Matter - Materials Science
Abstract

High pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here we report the synthesis at ~90 GPa of novel beryllium polynitrides, monoclinic and triclinic BeN4. The triclinic phase, upon decompression to ambient conditions, transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds consisting of polyacetylene-like nitrogen chains with conjugated {\pi}-systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The BeN4 layer, i.e. beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions.

Published
2020
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3. Insulator-metal transition in liquid hydrogen and deuterium

Author

Jiang, Shuqing, Holtgrewe, Nicholas, Geballe, Zachary M., Lobanov, Sergey S., Mahmood, Mohammad F., McWilliams, R. Stewart, and Goncharov, Alexander F.

Subjects
Condensed Matter - Materials Science
Abstract

The insulator-to-metal transition in dense fluid hydrogen is an essential phenomenon to understand gas giant planetary interiors and the physical and chemical behavior of highly compressed condensed matter. Using fast laser spectroscopy techniques to probe hydrogen and deuterium precompressed in a diamond anvil cell and laser heated on microsecond timescales, we observe an onset of metal-like reflectivity in the visible spectral range at P>150 GPa and T>3000 K. The reflectance increases rapidly with decreasing photon energy indicating free-electron metallic behavior with a plasma edge in the visible spectral range at high temperatures. The reflectivity spectra also suggest much longer electronic collision time (>1 fs) than previously inferred, implying that metallic hydrogens at the conditions studied are not in the regime of saturated conductivity (Mott-Ioffe-Regel limit). Combined with previously reported data, our results suggest the existence of a semiconducting intermediate fluid hydrogen state en route to metallization., Comment: 23 pages, 15 figures

Published
2018

4. Metallization and molecular dissociation of dense fluid nitrogen

Author

Jiang, Shuqing, Holtgrewe, Nicholas, Lobanov, Sergey S., Su, Fuhai, Mahmood, Mohammad F., McWilliams, R. Stewart, and Goncharov, Alexander F.

Subjects
Condensed Matter - Materials Science, aps.org
Abstract

Diatomic nitrogen is an archetypal molecular system known for its exceptional stability and complex behavior at high pressures and temperatures, including rich solid polymorphism, formation of energetic states, and an insulator-to-metal transformation coupled to a change in chemical bonding. However, the thermobaric conditions of the fluid molecular-polymer phase boundary and associated metallization have not been experimentally established. Here, by applying dynamic laser heating of compressed nitrogen and using fast optical spectroscopy to study electronic properties, we observe a transformation from insulating (molecular) to conducting dense fluid nitrogen at temperatures that decrease with pressure, and establish that metallization, and presumably fluid polymerization, occurs above 125 GPa at 2500 K. Our observations create a better understanding of the interplay between molecular dissociation, melting, and metallization revealing features that are common in simple molecular systems., Comment: 19 pages, 9 figures

Published
2017
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5. High‐pressure Synthesis of Cobalt Polynitrides: Unveiling Intriguing Crystal Structures and Nitridation Behavior.

Author

Chen, Huawei, Bykov, Maxim, Batyrev, Iskander G., Brüning, Lukas, Bykova, Elena, Mahmood, Mohammad F., Chariton, Stella, Prakapenka, Vitali B., Fedotenko, Timofey, Liermann, Hanns‐Peter, Glazyrin, Konstantin, Steele, Andrew, and Goncharov, Alexander F.

Subjects
DIAMOND anvil cell, NITRIDATION, CRYSTAL structure, COBALT, ENERGY development, RAMAN spectroscopy
Abstract

In this study, we conduct extensive high‐pressure experiments to investigate phase stability in the cobalt‐nitrogen system. Through a combination of synthesis in a laser‐heated diamond anvil cell, first‐principles calculations, Raman spectroscopy, and single‐crystal X‐ray diffraction, we establish the stability fields of known high‐pressure phases, hexagonal NiAs‐type CoN, and marcasite‐type CoN2 within the pressure range of 50–90 GPa. We synthesize and characterize previously unknown nitrides, Co3N2, Pnma‐CoN and two polynitrides, CoN3 and CoN5, within the pressure range of 90–120 GPa. Both polynitrides exhibit novel types of polymeric nitrogen chains and networks. CoN3 feature branched‐type nitrogen trimers (N3) and CoN5 show π‐bonded nitrogen chain. As the nitrogen content in the cobalt nitride increases, the CoN6 polyhedral frameworks transit from face‐sharing (in CoN) to edge‐sharing (in CoN2 and CoN3), and finally to isolated (in CoN5). Our study provides insights into the intricate interplay between structure evolution, bonding arrangements, and high‐pressure synthesis in polynitrides, expanding the knowledge for the development of advanced energy materials [ABSTRACT FROM AUTHOR]

Published
2024
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11. Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN2: High-Pressure Route to Pentagonal 2D Materials

Author

Bykov, Maxim, primary, Bykova, Elena, additional, Ponomareva, Alena V., additional, Tasnádi, Ferenc, additional, Chariton, Stella, additional, Prakapenka, Vitali B., additional, Glazyrin, Konstantin, additional, Smith, Jesse S., additional, Mahmood, Mohammad F., additional, Abrikosov, Igor A., additional, and Goncharov, Alexander F., additional

Published
2021
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13. Realization of an Ideal Cairo Tessellation in Nickel Diazenide NiN2: High-Pressure Route to Pentagonal 2D Materials

Author

Bykov, Maxim, Bykova, Elena, Ponomareva, Alena V, Tasnadi, Ferenc, Chariton, Stella, Prakapenka, Vitali B., Glazyrin, Konstantin, Smith, Jesse S., Mahmood, Mohammad F., Abrikosov, Igor, Goncharov, Alexander F., Bykov, Maxim, Bykova, Elena, Ponomareva, Alena V, Tasnadi, Ferenc, Chariton, Stella, Prakapenka, Vitali B., Glazyrin, Konstantin, Smith, Jesse S., Mahmood, Mohammad F., Abrikosov, Igor, and Goncharov, Alexander F.

Abstract

Most of the studied two-dimensional (2D) materials are based on highly symmetric hexagonal structural motifs. In contrast, lower-symmetry structures may have exciting anisotropic properties leading to various applications in nano-electronics. In this work we report the synthesis of nickel diazenide NiN2 which possesses atomic-thick layers comprised of Ni2N3 pentagons forming Cairo-type tessellation. The layers of NiN2 are weakly bonded with the calculated exfoliation energy of 0.72 J/m(2), which is just slightly larger than that of graphene. The compound crystallizes in the space group of the ideal Cairo tiling (P4/mbm) and possesses significant anisotropy of elastic properties. The single-layer NiN2 is a direct-band-gap semiconductor, while the bulk material is metallic. This indicates the promise of NiN2 to be a precursor of a pentagonal 2D material with a tunable direct band gap., Funding Agencies|Army Research Office; Russian Science FoundationRussian Science Foundation (RSF) [18-12-00492]; Ministry of Science and Higher Education of the Russian Federation [K22020-026, 211]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [KAW-2018.0194]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; SeRC, the Swedish Research Council (VR) [2019-05600]; Vinnova VINN Excellence Center Functional Nanoscale Materials (FunMat-2) Grant [201605156]; Swedish Research CouncilSwedish Research CouncilEuropean Commission [2016-07213]; National Science Foundation.Earth SciencesNational Science Foundation (NSF) [EAR.1634415]; Department of Energy-GeosciencesUnited States Department of Energy (DOE) [DE-FG0294ER14466]; DOENNSAs Office of Experimental Sciences; DOE Office of ScienceUnited States Department of Energy (DOE) [DEAC02-06CH11357]; [W911NF-192-0172]

Published
2021
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14. Stabilization of Polynitrogen Anions in Tantalum-Nitrogen Compounds at High Pressure

Author

Bykov, Maxim, Bykova, Elena, Ponomareva, Alena V., Abrikosov, Igor, Chariton, Stella, Prakapenka, Vitali B., Mahmood, Mohammad F., Dubrovinsky, Leonid, Goncharov, Alexander F., Bykov, Maxim, Bykova, Elena, Ponomareva, Alena V., Abrikosov, Igor, Chariton, Stella, Prakapenka, Vitali B., Mahmood, Mohammad F., Dubrovinsky, Leonid, and Goncharov, Alexander F.

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 [N-5(5-)](infinity). Apart from that we discover two novel Ta-N compounds: TaN4 with finite N-4(4-) chains and the incommensurately modulated compound TaN2-x, which is recoverable at ambient conditions., Funding Agencies|Ministry of Science and Higher Education of the Russian Federation [K2-2020-026]; SFO in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-AC02-06CH11357]; National Science Foundation - Earth SciencesNational Science Foundation (NSF) [EAR-1634415]; Department of Energy, GeosciencesUnited States Department of Energy (DOE) [DE-FG02-94ER14466]

Published
2021
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15. High-Pressure Synthesis of Dirac Materials: Layered van der Waals Bonded BeN4 Polymorph

Author

Bykov, Maxim, Fedotenko, Timofey, Chariton, Stella, Laniel, Dominique, Glazyrin, Konstantin, Hanfland, Michael, Smith, Jesse S., Prakapenka, Vitali B., Mahmood, Mohammad F., Goncharov, Alexander F., Ponomareva, Alena V, Tasnadi, Ferenc, Abrikossov, Alexei, Masood, Talha Bin, Hotz, Ingrid, Rudenko, Alexander N., Katsnelson, Mikhail I, Doubrovinckaia, Natalia, Dubrovinsky, Leonid, Abrikosov, Igor, Bykov, Maxim, Fedotenko, Timofey, Chariton, Stella, Laniel, Dominique, Glazyrin, Konstantin, Hanfland, Michael, Smith, Jesse S., Prakapenka, Vitali B., Mahmood, Mohammad F., Goncharov, Alexander F., Ponomareva, Alena V, Tasnadi, Ferenc, Abrikossov, Alexei, Masood, Talha Bin, Hotz, Ingrid, Rudenko, Alexander N., Katsnelson, Mikhail I, Doubrovinckaia, Natalia, Dubrovinsky, Leonid, and Abrikosov, Igor

Abstract

High-pressure chemistry is known to inspire the creation of unexpected new classes of compounds with exceptional properties. Here, we employ the laser-heated diamond anvil cell technique for synthesis of a Dirac material BeN4. A triclinic phase of beryllium tetranitride tr-BeN4 was synthesized from elements at similar to 85 GPa. Upon decompression to ambient conditions, it transforms into a compound with atomic-thick BeN4 layers interconnected via weak van der Waals bonds and consisting of polyacetylene-like nitrogen chains with conjugated pi systems and Be atoms in square-planar coordination. Theoretical calculations for a single BeN4 layer show that its electronic lattice is described by a slightly distorted honeycomb structure reminiscent of the graphene lattice and the presence of Dirac points in the electronic band structure at the Fermi level. The BeN4 layer, i.e., beryllonitrene, represents a qualitatively new class of 2D materials that can be built of a metal atom and polymeric nitrogen chains and host anisotropic Dirac fermions., Funding Agencies|Army Research Office; Deutsche Forschungsgemeinschaft (DFG)German Research Foundation (DFG) [DU 954-11/1, DU 393-9/2, DU 393-13/1]; Federal Ministry of Education and Research, Germany (BMBF)Federal Ministry of Education & Research (BMBF) [05K19WC1]; Alexander von Humboldt FoundationAlexander von Humboldt Foundation; Russian Science FoundationRussian Science Foundation (RSF) [18-12-00492]; Ministry of Science and Higher Education of the Russian Federation of Increase Competitiveness Program of NUST MISIS [K2-2020-026, 211]; Knut and Alice Wallenberg Foundation (Wallenberg Scholar Grant) [KAW-2018.0194]; Swedish Government Strategic Research Areas in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]; SeRCAgency for Science Technology & Research (ASTAR); Swedish Research Council (VR)Swedish Research Council [2019-05600]; Vinnova VINN Excellence Center Functional Nanoscale Materials (FunMat-2) [2016-05156]; Swedish Research CouncilSwedish Research CouncilEuropean Commission [2016-07213]; JTC-FLAGERA Project GRANSPORT; National Science Foundation-Earth SciencesNational Science Foundation (NSF) [EAR-1634415]; Department of Energy-GeosciencesUnited States Department of Energy (DOE) [DE-FG0294ER14466]; DOENNSAs Office of Experimental Sciences; DOE Office of ScienceUnited States Department of Energy (DOE) [DE-AC02-06CH11357]; [W911NF-19-2-0172]

Published
2021
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16. High-Pressure Synthesis of Dirac Materials: Layered van der Waals Bonded BeN4 Polymorph

Author

Bykov, Maxim, primary, Fedotenko, Timofey, additional, Chariton, Stella, additional, Laniel, Dominique, additional, Glazyrin, Konstantin, additional, Hanfland, Michael, additional, Smith, Jesse S., additional, Prakapenka, Vitali B., additional, Mahmood, Mohammad F., additional, Goncharov, Alexander F., additional, Ponomareva, Alena V., additional, Tasnádi, Ferenc, additional, Abrikosov, Alexei I., additional, Bin Masood, Talha, additional, Hotz, Ingrid, additional, Rudenko, Alexander N., additional, Katsnelson, Mikhail I., additional, Dubrovinskaia, Natalia, additional, Dubrovinsky, Leonid, additional, and Abrikosov, Igor A., additional

Published
2021
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19. Cover Feature: High‐pressure Synthesis of Cobalt Polynitrides: Unveiling Intriguing Crystal Structures and Nitridation Behavior (Chem. Eur. J. 32/2024).

Author

Chen, Huawei, Bykov, Maxim, Batyrev, Iskander G., Brüning, Lukas, Bykova, Elena, Mahmood, Mohammad F., Chariton, Stella, Prakapenka, Vitali B., Fedotenko, Timofey, Liermann, Hanns‐Peter, Glazyrin, Konstantin, Steele, Andrew, and Goncharov, Alexander F.

Subjects
CRYSTAL structure, NITRIDATION, COBALT, SPECTRAL imaging
Abstract

This article discusses the discovery of cobalt polynitrides through high-pressure synthesis using laser-heated diamond anvil cells. The researchers found that the degree of nitrogen polymerization increased with increasing pressure. By utilizing single-crystal synchrotron X-ray diffraction and micro-Raman imaging spectroscopy, the crystal structures of these nitrides were elucidated. The study also suggests the possibility of recovering these materials under ambient conditions. The full research article provides more detailed information on the topic. [Extracted from the article]

Published
2024
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21. Stabilization of pentazolate anions in the high-pressure compounds Na2N5 and NaN5 and in the sodium pentazolate framework NaN5·N2.

Author

Bykov, Maxim, Bykova, Elena, Chariton, Stella, Prakapenka, Vitali B., Batyrev, Iskander G., Mahmood, Mohammad F., and Goncharov, Alexander F.

Subjects
SODIUM azide, SODIUM compounds, ANIONS, ENERGY density
Abstract

Synthesis and characterization of nitrogen-rich materials is important for the design of novel high energy density materials due to extremely energetic low-order nitrogen–nitrogen bonds. The balance between the energy output and stability may be achieved if polynitrogen units are stabilized by resonance as in cyclo-N5− pentazolate salts. Here we demonstrate the synthesis of three oxygen-free pentazolate salts Na2N5, NaN5 and NaN5·N2 from sodium azide NaN3 and molecular nitrogen N2 at ∼50 GPa. NaN5·N2 is a metal-pentazolate framework (MPF) obtained via a self-templated synthesis method with nitrogen molecules being incorporated into the nanochannels of the MPF. Such self-assembled MPFs may be common in a variety of ionic pentazolate compounds. The formation of Na2N5 demonstrates that the cyclo-N5 group can accommodate more than one electron and indicates the great accessible compositional diversity of pentazolate salts. [ABSTRACT FROM AUTHOR]

Published
2021
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22. Insulator-metal transition in liquid hydrogen and deuterium

Author

Aleksandr Fedorov, Mahmood, Mohammad F., Nicholas Holtgrewe, Stewart Mcwilliams, R., Lobanov, Sergey S., Shuqing Jiang, and Geballe, Zachary M.

Subjects
Condensed Matter - Materials Science, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

The insulator-to-metal transition in dense fluid hydrogen is an essential phenomenon to understand gas giant planetary interiors and the physical and chemical behavior of highly compressed condensed matter. Using fast laser spectroscopy techniques to probe hydrogen and deuterium precompressed in a diamond anvil cell and laser heated on microsecond timescales, we observe an onset of metal-like reflectivity in the visible spectral range at P>150 GPa and T>3000 K. The reflectance increases rapidly with decreasing photon energy indicating free-electron metallic behavior with a plasma edge in the visible spectral range at high temperatures. The reflectivity spectra also suggest much longer electronic collision time (>1 fs) than previously inferred, implying that metallic hydrogens at the conditions studied are not in the regime of saturated conductivity (Mott-Ioffe-Regel limit). Combined with previously reported data, our results suggest the existence of a semiconducting intermediate fluid hydrogen state en route to metallization., 23 pages, 15 figures

Published
2018

33. Optical soliton perturbation in magneto-optic waveguides

Author

Biswas, Anjan, primary, Arnous, Ahmed H., additional, Ekici, Mehmet, additional, Sonmezoglu, Abdullah, additional, Seadawy, Aly R., additional, Zhou, Qin, additional, Mahmood, Mohammad F., additional, Moshokoa, Seithuti P., additional, and Belic, Milivoj, additional

Published
2018
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34. Structural and chemical properties of the nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate under pressure.

Author

McWilliams, R. Stewart, Kadry, Yasmin, Mahmood, Mohammad F., Goncharov, Alexander F., and Ciezak-Jenkins, Jennifer

Subjects
MOLECULAR structure, TETRAZOLES, NITROGEN, GUANIDINE, HYDROGEN bonding, HIGH pressure (Science), SCIENTIFIC observation
Abstract

The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate C3H12N12O2 (TAG-MNT) have been investigated at room pressure and under high pressure isothermal compression using powder x-ray diffraction and Raman and infrared spectroscopy. A stiffening of the equation of state and concomitant structural relaxation between 6 and 14 GPa are found to correlate with Raman mode disappearances, frequency discontinuities, and changes in the pressure dependence of modes. These observations manifest the occurrence of a reversible martensitic structural transformation to a new crystalline phase. The onset and vanishing of Fermi resonance in the nitrimine group correlate with the stiffening of the equation of state and phase transition, suggesting a possible connection between these phenomena. Beyond 15 GPa, pressure induces irreversible chemical reactions, culminating in the formation of a polymeric phase by 60 GPa. [ABSTRACT FROM AUTHOR]

Published
2012
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41. Metallization and molecular dissociation of dense fluid nitrogen.

Author

Shuqing Jiang, Holtgrewe, Nicholas, Lobanov, Sergey S., Fuhai Su, Mahmood, Mohammad F., McWilliams, R. Stewart, and Goncharov, Alexander F.

Abstract

Diatomic nitrogen is an archetypal molecular system known for its exceptional stability and complex behavior at high pressures and temperatures, including rich solid polymorphism, formation of energetic states, and an insulator-to-metal transformation coupled to a change in chemical bonding. However, the thermobaric conditions of the fluid molecular--polymer phase boundary and associated metallization have not been experimentally established. Here, by applying dynamic laser heating of compressed nitrogen and using fast optical spectroscopy to study electronic properties, we observe a transformation from insulating (molecular) to conducting dense fluid nitrogen at temperatures that decrease with pressure and establish that metallization, and presumably fluid polymerization, occurs above 125 GPa at 2500 K. Our observations create a better understanding of the interplay between molecular dissociation, melting, and metallization revealing features that are common in simple molecular systems. [ABSTRACT FROM AUTHOR]

Published
2018
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42. Spectroscopy, kinetics, and laser effects of HgBr (B-state) formation due to collisions of CO+ ions with CH3HgBr.

Author

Mahmood, Mohammad F.

Subjects
*COLLISIONS (Nuclear physics), *EMISSION spectroscopy
Abstract

Reports on the dissociative excitation of the HgBr (B-X) band system and atomic mercury lines during collisions involving CO[sup+] ions with CH[sub3]HgBr. Diagram of the experimental setup; Information on the emission spectra observed during collisions.

Published
1989
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47. Structural and Chemical Properties of the Nitrogen-Rich Energetic Material Triaminoguanidinium 1-methyl-5-nitriminotetrazolate under Pressure

Author

ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD SURVIVABILITY-LETHALITY ANALYSIS DIR/ INFORMATION AND ELECTRONIC PROTECTION DIV, McWilliams, R S, Kadry, Yasmin, Mahmood, Mohammad F, Goncharov, Alexander F, Ciezak-Jenkins, Jennifer, ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD SURVIVABILITY-LETHALITY ANALYSIS DIR/ INFORMATION AND ELECTRONIC PROTECTION DIV, McWilliams, R S, Kadry, Yasmin, Mahmood, Mohammad F, Goncharov, Alexander F, and Ciezak-Jenkins, Jennifer

Abstract

The structural and chemical properties of the bi-molecular, hydrogen-bonded, nitrogen-rich energetic material triaminoguanidinium 1-methyl-5-nitriminotetrazolate C3H12N12O2 (TAG-MNT) have been investigated at room pressure and under high pressure isothermal compression using powder x-ray diffraction and Raman and infrared spectroscopy. A stiffening of the equation of state and concomitant structural relaxation between 6 and 14 GPa are found to correlate with Raman mode disappearances, frequency discontinuities, and changes in the pressure dependence of modes. These observations manifest the occurrence of a reversible martensitic structural transformation to a new crystalline phase. The onset and vanishing of Fermi resonance in the nitrimine group correlate with the stiffening of the equation of state and phase transition, suggesting a possible connection between these phenomena. Beyond 15 GPa, pressure induces irreversible chemical reactions, culminating in the formation of a polymeric phase by 60 GPa., Published in the Journal of Chemical Physics, v137 article ID 054501, 1 Aug 2012. Prepared in cooperation with Howard University, Washington, DC and the Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC. Sponsored in part by DoE DE-FC52-08NA28554, DE-FG02-94ER14466, DE-AC02-06CH11357, DE-AC02-98CH10886 and DE-FC03-03N00144.

Published
2012

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