Crystal Structure of NbOBr<sub>2</sub>

Beck, Johannes; Kusterer, Christian

doi:10.1002/zaac.200600171

Cited by 13 publications

(10 citation statements)

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“…It was shown that the NbCl 4 O 2 octahedra are distorted by the formation of NbϪNb bonds and alternating NbϪO distances. This model was confirmed for NbOBr 2 by Beck et al [11]. In this case, too, single crystals were obtained as a by-product from the reaction of NbOBr 3 and InBr.…”

Section: Introductionsupporting

confidence: 71%

“…But the values of the displacement parameters and out-of-centre position of Nb are very similar to our results on NbOI 3 , so the model in C2 is probably correct. The non-centrosymmetric model (C2) with alternating NbϪNb and NbϪO distances was recently confirmed for NbOBr 2 [11].…”

Section: Comparison To Nbocl 3 and Further Oxidehalides With Chain Stmentioning

confidence: 71%

“…The initial goal was the synthesis of CsNbOI 4 [8]. To this CsI (0.667 mmol), Nb 2 O 5 (0.133 mmol), Nb (0.4 mmol) and I 2 (1 mmol) were sealed in an evacuated quartz ampoule (length 10 cm, diameter 1.5 cm) and submitted to the following temperature programme (heating/cooling rates in italics, dwell time in [14] 0.0322 / 0.0 0.038 / 0.0 0.0 / 0.0 Extinction correction [14] 0.00000(13) 0.00000(45) 0.0014(7) Flack parameter [14] Ϫ0.05 (11) Ϫ0.02(44) Goodness of fit 0.984 1.051 0.679 Residual electron density ϩ 1.37 / Ϫ1.13 / 0.25 e Ϫ /Å 3 ϩ 0.92 / Ϫ1.23 / 0.23 e Ϫ /Å 3 ϩ 1.11 / Ϫ1.31 / 0.31 e Ϫ /Å 3 (max., min., sigma) www.zaac.wiley-vch.de…”

Section: Nboimentioning

confidence: 99%

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Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Hartwig

Hillebrecht

2007

Zeitschrift anorg allge chemie

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NbOI 3 was obtained from a reaction of Nb 2 O 5 , Nb, and I 2 . Single crystals free from disorder were a by-product from a reaction with additional CsI. The monoclinic crystal structure (C2, a ϭ 14.624(3) Å , b ϭ 3.9905(8) Å , c ϭ 12.602(3) Å , β ϭ 120.4(3)°, Z ϭ 4, R 1 (F) ϭ 0.0368, wR 2 (F 2 ) ϭ 0.0804) represents a new structure type which is built up by distorted octahedral NbI 4 O 2 with unequal O-atoms in trans-position. The octahedra are linked to dimers by a common edge of iodine atoms and to double chains by the apical oxygen atoms. A non-centrosymmetric structure results because the 115 short NbϪO distances point to the same direction and the polar double chains are parallel. The crystal structure of NbOBr 3 (NbOCl 3 -type, P42 1 m, a ϭ 11.635(6) Å , c ϭ 3.953(2) Å , R 1 (F) ϭ 0.082, wR 2 (F 2 ) ϭ 0.174) shows the same polar double chains but the dimeric units Nb 2 Br 6 O 2 are orthogonal.

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Section: Introductionsupporting

confidence: 71%

Section: Comparison To Nbocl 3 and Further Oxidehalides With Chain Stmentioning

confidence: 71%

Section: Nboimentioning

confidence: 99%

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Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Hartwig

Hillebrecht

2007

Zeitschrift anorg allge chemie

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“…As determined by experimental structural characterizations, [29][30][31] bulk NbOX 2 can crystalize in a ferroelectric C2 phase with monoclinic symmetry, where Nb cations exhibit non-zero off-center displacement along the Nb-O-Nb atomic chain direction (b axis). In our work, in order to explore all possible NbOX 2 polar configurations, we choose the Nb polar-distortion free, centrosymmetric C2/m phase (ground state structures for MoOCl 2 34 and TaOI 2 35 ) as the paraelectric (PE) reference for bulk NbOX 2 .…”

Section: Resultsmentioning

confidence: 99%

“…Bulk NbOX 2 have been synthesized since the 1960s, 27,28 and they can be potentially exfoliated into 2D layered forms. Despite their structural polarities at room temperature, [28][29][30][31] NbOX 2 have not been considered or investigated as 2D layered ferroelectrics. Except for earlier tight-binding band structure calculations, 32 accurate predictions regarding electronic and FE properties for NbOX 2 bulk and 2D layers have never been reported.…”

Section: Introductionmentioning

confidence: 99%

Niobium oxide dihalides NbOX₂: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

et al. 2019

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2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

Fang

Wang

et al. 2021

Advanced Materials

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induced diodes, [23,24] polarization-sensitive photodetectors, [25,26] synaptic-neuromorphic devices, [27] etc. Although the research on anisotropic 2D materials is progressing rapidly, it is still in its infancy as a whole. Therefore, developing new materials and exploring their anisotropic physical properties and functional devices are of great significance to the development of science and technology.Recently, layered transition metal oxide dihalides MOX 2 (M = V, Nb, Ta, Mo; X = Cl, Br, I) have gained increasing attention among materials scientists due to their chiral crystal structure and unique physical properties. [28][29][30][31][32][33] Among them, NbOI 2 has a low-symmetry monoclinic structure (space group C2), in which Nb atoms shift away from the center of [NbO 2 I 4 ] octahedra connected by sharing I-I edges and cornered O atoms along the c-and b-axes. Various connection modes enable NbOI 2 strong anisotropic physical properties and highly dispersed band structure. The simulated optical absorption coefficient along the c-axis (α c ) is an order of magnitude higher than that along the b-axis (α b ). [34] Consequently, the NbOI 2 is expected to exhibit unique in-plane anisotropy. However, until now, the preparation and basic properties of 2D NbOI 2 crystals have not been thoroughly investigated, and in particular, the in-plane anisotropy caused by its low-symmetry structure is still unclear.Here, we introduce a kind of transition metal oxide dihalides, NbOI 2 , into the 2D materials family with experimental demonstration of strong in-plane anisotropy. Few-layer and monolayer NbOI 2 crystals were obtained through mechanical exfoliation, and these crystals showed large second harmonic generation (SHG) response, verifying its noncentrosymmetric crystal structure. The strong in-plane anisotropy of phonon vibration in 2D NbOI 2 crystals was observed by using angleresolved polarized Raman measurements. The anisotropic electronic dispersion around the Fermi surfaces leads to the strong anisotropy of optical absorbance with an anisotropic factor of 1.75. In addition, highly anisotropic in-plane electrical resistance with a factor of 1.34 and photoresponsivity with a factor of 1.7 were demonstrated in 2D NbOI 2 crystals. These findings indicate that the 2D NbOI 2 crystal can serve as a promising candidate in anisotropic electronic and optoelectronic devices. Results and DiscussionBulk NbOI 2 belongs to the monoclinic space group C2 (No. 5) with a = 15.18 Å, b = 3.92 Å, c = 7.52 Å, β = 105.5°. Figure 1a Exploring in-plane anisotropic 2D materials is of great significance to the fundamental studies and further development of polarizationsensitive optoelectronics. Herein, chiral niobium oxide diiodide (NbOI 2 ) is introduced into the intriguing anisotropic 2D family with the experimental demonstration of anisotropic optical and electrical properties. 2D NbOI 2 crystals exhibit highly anisotropic dispersed band structures around the Fermi surface and strong in-plane anisotropy of phonon vibrations owing to the diff...

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Crystal Structure of NbOBr₂

Cited by 13 publications

References 5 publications

Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Niobium oxide dihalides NbOX₂: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

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Crystal Structure of NbOBr2

Cited by 13 publications

References 5 publications

Crystal Structures of NbOI3 and NbOBr3 – Polar Double Chains in Different Non‐centrosymmetric Structures

Crystal Structures of NbOI3 and NbOBr3 – Polar Double Chains in Different Non‐centrosymmetric Structures

Niobium oxide dihalides NbOX2: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

2D NbOI2: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties

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Crystal Structure of NbOBr₂

Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Crystal Structures of NbOI₃ and NbOBr₃ – Polar Double Chains in Different Non‐centrosymmetric Structures

Niobium oxide dihalides NbOX₂: a new family of two-dimensional van der Waals layered materials with intrinsic ferroelectricity and antiferroelectricity

2D NbOI₂: A Chiral Semiconductor with Highly In‐Plane Anisotropic Electrical and Optical Properties