Pressure-Induced Symmetry-Lowering Transition in Dense Nitrogen to Layered Polymeric Nitrogen (LP-N) with Colossal Raman Intensity

Tomasino, Dane; Kim, Minseob; Smith, Jesse S.; Yoo, Choong‐Shik

doi:10.1103/physrevlett.113.205502

Cited by 184 publications

(181 citation statements)

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“…The first polymeric crystalline structure of N obtained experimentally is the cubic gauche phase -cg-N, which was first reported by 14,26 at pressure and temperature over 110 GPa and 2000 K. Later experiments managed to synthesize cg-N also at different conditions 15,25,[27][28][29] . This insulating phase yields unusual structure with I2 1 3 symmetry, which is composed of fused N 10 rings connected in a way that maximizes the number of energetically favorable gauche dihedral angles (of lp-N-N-lp with lp being the electron lone-pair), which minimize the effect of mutual lp repulsion 5,30 .…”

Section: Introductionmentioning

confidence: 87%

Transformation pathways in high-pressure solid nitrogen: From molecular N2 to polymeric cg-N

Plašienka

Martoňák

2015

The Journal of Chemical Physics

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The transformation pathway in high-pressure solid nitrogen from N 2 molecular state to polymeric cg-N phase was investigated by means of ab initio molecular dynamics and metadynamics simulations. In our study, we observed a transformation mechanism starting from molecular Immm phase that initiated with formation of trans-cis chains. These chains further connected within layers and formed a chain-planar state, which we describe as a mixture of two crystalline structures -trans-cis chain phase and planar phase, both with P nma symmetry. This mixed state appeared in molecular dynamics performed at 120 GPa and 1500 K and in the metadynamics run at 110 GPa and 1500 K, where the chains continued to reorganize further and eventually formed cg-N. During separate simulations, we also found two new phases -molecular P 2 1 /c and two-threecoordinated chain-like Cm. The transformation mechanism heading towards cg-N can be characterized as a progressive polymerization process passing through several intermediate states of variously connected transcis chains. In the final stage of the transformation chains in the layered form rearrange collectively and develop new intraplanar as well as interplanar bonds leading to the geometry of cg-N. Chains with alternating trans and cis conformation were found to be the key entity -structural pattern governing the dynamics of the simulated molecular-polymeric transformation in compressed nitrogen.

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Section: Introductionmentioning

confidence: 87%

Transformation pathways in high-pressure solid nitrogen: From molecular N2 to polymeric cg-N

Plašienka

Martoňák

2015

The Journal of Chemical Physics

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“…In turn, the limited findings advocate for searching these predicted structures and gaining systematic insights into those unusual transformations. Importantly, these low Z extended solids are likely high energy density solids with energy content of ~10-100 kJ/g and may also exhibit other novel properties such as super hardness, superconductivity and nonlinear optical properties [4,17,18]. 2 ) 4 ), advocating further studies.…”

Section: Chemistry In Dense Solidsmentioning

confidence: 99%

“…[4]. Singly bonded LP-N was synthesized by laser heating nitrogen samples at pressures between 125-175 GPa and temperatures above 2000 K, which formed together with cg-N and amorphous N (Fig.…”

Section: Singly Bonded Layered Polymeric Nitrogen (Lp-n)mentioning

confidence: 99%

“…As a result, a large number (over dozen) of extended nitrogen structures have been predicted to be stable in various forms; yet, the cg-N was the only extended phase of nitrogen discovered until very recently. Recently, we discovered new singly bonded extended nitrogen [4], synthesized using laser-heated diamond anvil cells at pressures between 120-180 GPa, well above the stability field of cg-N. This new phase was characterized by its singly bonded, layered polymeric (LP) structure similar to the predicted Pba2 and two colossal Raman bands arising from two groups of highly polarized nitrogen atoms in the bulk and surface of the layer.…”

Section: Introductionmentioning

confidence: 99%

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High energy density nitrogen-rich extended solids

Yoo¹,

Tomasino²,

Smith³

et al. 2017

AIP Conference Proceedings

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Abstract.Many simple molecules such as N 2 and CO 2 have the potential to form extended "polymeric" solids under extreme conditions, which can store a large sum of chemical energy in its three-dimensional network structures made of strong covalent bonds. Diatomic nitrogen is particularly of interest because of the uniquely large energy difference between the single (160 kJ/mol) and triple (950 kJ/mol) bonds. As such, the transformation of singly bonded polymeric nitrogen back to triply bonded diatomic nitrogen molecules can release large energy (~33 kJ/cm 3 -three times that of HMX) without any negative environmental impact. Therefore, the goal of the present study has been to investigate the transformation of nitrogen and nitrogen-rich compounds to new singly bonded nitrogen-rich solids at high pressures and temperatures, using heated diamond anvil cells, Raman spectroscopy, and third-generation synchrotron x-ray diffraction. Recently, we have found a new form of singly bonded layered polymeric nitrogen (LP-N), synthesized in the stability pressure-temperature field higher than that of cg-N. This new phase is characterized by a 2D layered structure similar to the predicted Pba2 and two colossal Raman bands, arising from two groups of highly polarized nitrogen atoms. This result also provides a new constraint for the nitrogen phase diagram, highlighting an unusual symmetry lowering 3D cgto 2D LP-N transition and thereby the enhanced electrostatic contribution to the stabilization of this densely packed LP-N. In this paper, we will review this finding of LP-N, update the phase diagram of nitrogen, and offer a chemistry view of pressure-induced transformations in dense molecular solids.

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“…The article by Yoo 16 in this issue draws from the behavior of ices, 17 CO 2 , 18,19 and nitrogen [20][21][22] to illustrate some of the structures that have been discovered and their associated properties. This work opens up the opportunity to make novel compounds with, for example, new piezoelectric, ferromagnetic, or superconducting functionality, 23,24 or extremely high energy densities.…”

Section: Superhigh Pressuresmentioning

confidence: 99%