Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN<sub>3</sub>

Schmidt, Carsten L.; Dinnebiér, Robert E.; Wedig, Ulrich; Jansen, Martin

doi:10.1021/ic061963n

Cited by 38 publications

(33 citation statements)

References 59 publications

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“…Such bond multiplicity (22) of carbon, although absent in the well-known diamond, graphite and graphene, has been found in a number of carbon structures with different dimensionalities (6-8, 22, 23) and is of general chemical interest as it leads to intermediate valency (23). Interestingly, we note that penta-graphene resembles the structure of experimentally identified layered silver azide (AgN 3 ) (24). By replacing the N 3 moieties and Ag atoms with the triconnected C dimers and tetra-connected C atoms, respectively, the geometry of pentagraphene can be realized.…”

Section: Significancesupporting

confidence: 52%

Penta-graphene: A new carbon allotrope

Zhang

Zhou

Wang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

1,280

921

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A 2D metastable carbon allotrope, penta-graphene, composed entirely of carbon pentagons and resembling the Cairo pentagonal tiling, is proposed. State-of-the-art theoretical calculations confirm that the new carbon polymorph is not only dynamically and mechanically stable, but also can withstand temperatures as high as 1000 K. Due to its unique atomic configuration, penta-graphene has an unusual negative Poisson's ratio and ultrahigh ideal strength that can even outperform graphene. Furthermore, unlike graphene that needs to be functionalized for opening a band gap, penta-graphene possesses an intrinsic quasi-direct band gap as large as 3.25 eV, close to that of ZnO and GaN. Equally important, penta-graphene can be exfoliated from T12-carbon. When rolled up, it can form pentagon-based nanotubes which are semiconducting, regardless of their chirality. When stacked in different patterns, stable 3D twin structures of T12-carbon are generated with band gaps even larger than that of T12-carbon. The versatility of penta-graphene and its derivatives are expected to have broad applications in nanoelectronics and nanomechanics.carbon allotrope | carbon pentagon | stability | negative Poisson's ratio | electronic structure C arbon is one of the most versatile elements in the periodic table and forms a large number of allotropes ranging from the well-known graphite, diamond, C 60 fullerene (1), nanotube (2), and graphene (3) to the newly discovered carbon nanocone (4), nanochain (5), graphdiyne (6), as well as 3D metallic structures (7,8). The successful synthesis of graphene (3) has triggered considerable interest in exploring novel carbon-based nanomaterials. A wealth of 2D carbon allotropes beyond graphene has since been studied (see SI Appendix, Table S1 for details). Although some of these polymorphs such as graphdiyne (6) are metastable compared with graphene, they have been successfully synthesized. Moreover, some 2D carbon allotropes are predicted to exhibit remarkable properties that even outperform graphene, such as anisotropic Dirac cones (9), inherent ferromagnetism (10), high catalytic activity (6), and potential superconductivity related to the high density of states at the Fermi level (11). These results demonstrate that many of the novel properties of carbon allotropes are intimately related to the topological arrangement of carbon atoms and highlight the importance of structure-property relationships (12).Pentagons and hexagons are two basic building blocks of carbon nanostructures. From zero-dimensional nanoflakes or nanorings (13) to 1D nanotube, 2D graphene, and 3D graphite and metallic carbon phases (7,8), hexagon is the only building block. Extended carbon networks composed of only pentagons are rarely seen. Carbon pentagons are usually considered as topological defects or geometrical frustrations (14) as stated in the well-known "isolated pentagon rule" (IPR) (15) for fullerenes, where pentagons must be separated from each other by surrounding hexagons to reduce the steric stress. For instance, C 60 ...

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Section: Significancesupporting

confidence: 52%

Penta-graphene: A new carbon allotrope

Zhang

Zhou

Wang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

1,280

921

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“…The anomalous behavior (expansion) of a at high pressure is in accord with its anomalous behavior (shrink) at high temperature. 38 It may contribute to the detonation of AgN 3 on mechanical impact, where the necessary internal stress could result from the anomalous behavior of the lattice parameter a of orthorhombic AgN 3 . 38 The deformation of b is higher than of c (b shrinks 4% from ambient pressure to 2.3 GPa; while c shrinks 2%) at high pressure, which is also in accord with the higher deformation of b than of c at high temperature.…”

Section: Resultsmentioning

confidence: 99%

“…37 Upon heating from room temperature, its a-axis shows an anomalous behavior, since it shrinks with temperature. 38 AgN 3 exhibits an irreversible temperature-induced phase transition at 170 C to a monoclinic structure in P2 1 /c space group. 38 Despite the considerable previous studies on AgN 3 , no study on its high pressure structure has been reported yet.…”

Section: Introductionmentioning

confidence: 99%

“…38 AgN 3 exhibits an irreversible temperature-induced phase transition at 170 C to a monoclinic structure in P2 1 /c space group. 38 Despite the considerable previous studies on AgN 3 , no study on its high pressure structure has been reported yet. Comparing to its high temperature behavior, the possible phase transition and anomalous behavior of a-axis under high pressure are also interesting to be investigated.…”

Section: Introductionmentioning

confidence: 99%

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Phase transition and structure of silver azide at high pressure

Hou

Zhang

et al. 2011

Journal of Applied Physics

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Abstractilver azide (AgN 3 ) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters aand b, a 3° rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be inI4/mcm space group, with Ag at 4a, N 1 at 4d, and N 2 at 8h Wyckoff positions. Both of the two phases have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K OT = 39 ± 5 GPa with K OT ' = 10 ± 7 and K OT = 57 ± 2 GPa with K OT ' = 6.6 ± 0.2, respectively. KeywordsMechanical Engineering, Materials Science and Engineering, High pressure, Phase transitions, Active galaxies, Silver, Equations of state, X-ray diffraction, Polymers, Anisotropy, Elastic moduli, Magmatic magnetic minerals Disciplines Aerospace Engineering | Materials Science and Engineering | Mechanical Engineering CommentsThe following article appeared in Journal of Applied Physics 110 (2011) Silver azide (AgN 3 ) was compressed up to 51.3 GPa. The results reveal a reversible second-order orthorhombic-to-tetragonal phase transformation starting from ambient pressure and completing at 2.7 GPa. The phase transition is accompanied by a proximity of cell parameters a and b, a 3 rotation of azide anions, and a change of coordination number from 4-4 (four short, four long) to eight fold. The crystal structure of the high pressure phase is determined to be in I4/mcm space group, with Ag at 4a, N 1 at 4d, and N 2 at 8h Wyckoff positions. Both of the two phases have anisotropic compressibility: the orthorhombic phase exhibits an anomalous expansion under compression along a-axis and is more compressive along b-axis than c-axis; the tetragonal phase is more compressive along the interlayer direction than the intralayer directions. The bulk moduli of the orthorhombic and tetragonal phases are determined to be K OT ¼ 39 6 5 GPa with K OT ' ¼ 10 6 7 and K OT ¼ 57 6 2 GPa with K OT ' ¼ 6.6 6 0.2, respectively.

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“…Supplementary Table S1 gives the corresponding structural details. From the top view, we can see that both α-and β-SnX 2 2D crystals resemble the structure of experimentally identified layered silver azide 32 and are composed entirely of the pentagonal rings; they present an amazing pattern that is well known as Cairo pentagonal tiling. 33 The crystal structure of β-SnX 2 displays P-42 1 m symmetry (point group D 2d ) and a square lattice that contains two Sn and four X atoms in one unit cell.…”

Section: Resultsmentioning

confidence: 67%

Room temperature quantum spin Hall states in two-dimensional crystals composed of pentagonal rings and their quantum wells

Kou

et al. 2016

NPG Asia Mater

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Quantum spin Hall (QSH) insulators are a peculiar phase of matter exhibiting excellent quantum transport properties with potential applications in lower-power-consuming electronic devices. Currently, among all predicted or synthesized QSH insulators, square and hexagonal atomic rings are the dominant structural motifs, and QSH insulators composed of pentagonal rings have not yet been reported. Here, based on first-principles calculations, we predict a family of large-gap QSH insulators in SnX 2 (X = S, Se, or Te) two-dimensional (2D) crystals by the direct calculation of Z 2 topological invariants and edge states. Remarkably, in contrast to all known QSH insulators, the QSH insulators predicted here are composed entirely of pentagonal rings. Moreover, these systems can produce sizeable nontrivial gaps ranging from 121 to 224 meV, which is sufficiently large for practical applications at room temperature. Additionally, we propose a quantum well by sandwiching an SnTe 2 2D crystal between two BiOBiS 2 sheets and reveal that the considered 2D crystal remains topologically nontrivial with a sizeable gap. This finding demonstrates the robustness of its band topology against the effect of the substrate and provides a viable method for further experimental studies. The resultant Dirac surface states in three-dimensional (3D) TIs as well as the helical edge states in two-dimensional (2D) TIs are spin locked because of protection by time-reversal symmetry; thus, they are robust against perturbations. Particularly in 2D TIs, also known as quantum spin Hall (QSH) insulators, 3,4 all the low-energy scatterings of the edge states caused by the nonmagnetic defects are completely forbidden because the edge electrons can only propagate along two directions with opposite spins, which makes 2D TIs more suitable for lowpower-consuming applications than 3D TIs. Unfortunately, the material realization of 2D TIs is challenging: while 3D TIs have been discovered in many materials, such as the Bi 2 Se 3 family, 5,6 the experimental realization of 2D TIs is thus far limited to the HgTe/ CdTe 7 and InAs/GaSb 8 quantum wells. Moreover, the QSH effect in these two quantum wells can occur only at ultralow temperature (o10 K) because of their extremely small bulk band gaps, and this limitation greatly obstructs their possible applications. The search for new 2D TIs with large band gaps that could support room temperature applications has thus become critically important.

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Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN₃

Cited by 38 publications

References 59 publications

Penta-graphene: A new carbon allotrope

Penta-graphene: A new carbon allotrope

Phase transition and structure of silver azide at high pressure

Room temperature quantum spin Hall states in two-dimensional crystals composed of pentagonal rings and their quantum wells

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Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN3

Cited by 38 publications

References 59 publications

Penta-graphene: A new carbon allotrope

Penta-graphene: A new carbon allotrope

Phase transition and structure of silver azide at high pressure

Room temperature quantum spin Hall states in two-dimensional crystals composed of pentagonal rings and their quantum wells

Contact Info

Product

Resources

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Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN₃