Boron Nitride Allotropes Research Articles

Two-dimensional boron nitride allotrope Irida-B12N12 with 3-6-8 membered rings and wide-bandgap semiconducting properties

We present a novel two-dimensional (2D) boron nitride allotrope, Irida-B12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {B}_{{12}}$$\\end{document}N12\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {N}_{{12}}$$\\end{document} (Ir-BN), analogous to the all-carbon Irida-Graphene (Ir-G). The predicted structure of Ir-BN consists of alternating boron and nitrogen atoms, forming three distinct lattices with 3-, 6-, and 8-membered ring patterns. First-principles calculations based on density functional theory (DFT) formalism and ab initio molecular dynamics (AIMD) simulations were performed to investigate its structural, mechanical, electronic, and optical properties. The Ir-BN lattices exhibit good dynamical and thermal stability, supporting their viability as new 2D materials. Substantial anisotropy is observed in the mechanical properties, with in-plane stiffness ranging from 16 to 142 N/m, depending on the direction, and bulk moduli between 78 and 95 N/m. The electronic structure analysis reveals that Ir-BN is a wide-bandgap semiconductor, with band gaps ranging from 2.4 to 3.2 eV. The material shows optical activity particularly in the visible and ultraviolet regions.

A novel large-cell boron nitride polymorph

Through density functional theory simulations, the structural properties, stability, mechanical properties, elastic anisotropy as well as electronic properties for boron nitride allotropes with cubic structure, Pn-3n BN, are investigated in this work. Studying the phonon spectra, molecular dynamics as well as elastic constants of Pn-3n BN, it is found that porous Pn-3n BN is stable in dynamics, thermodynamics and mechanics. The B (bulk modulus), G (shear modulus) and E (Young's modulus) of Pn-3n BN are 64 GPa, 26 GPa and 69 GPa, respectively. The B/G (the ratio of bulk modulus to shear modulus) and v (Poisson's ratio) of Pn-3n BN are 2.43 and 0.319, respectively, which exhibit ductility. The three-dimensional surface construction for Young's modulus, the maximum and minimum of shear modulus, the maximum and minimum of Poisson's ratio of Pn-3n BN are all irregular spheres, indicating that Pn-3n BN has elastic anisotropy. The Emax/Emin of Pn-3n BN displays isotropy with 1.00 in (111) plane, and is not equal to 1.00 in other principal planes, showing anisotropy. The conduction band minimum (CBM) and the valence band maximum (VBM) of Pn-3n BN are both located at point G, and the band gap width of Pn-3n BN is 5.197 eV, from which Pn-3n BN is a wide band gap and direct band gap semiconductor material.

Exploring the potential of di-boron di-nitride monolayer (o-B2N2) as a K-ion battery anode: A DFT study

Due to favorable future use of electrochemical energy storage systems in portable electronic devices, these systems have received much attention. Employing these systems in "smart" clothes equipped with piezoelectric pieces to gain energy from body movement and roll-up displays is promising. Nevertheless, further development of these technologies is a significant challenge due to lack of appropriate battery electrodes that supply desirable electrochemical performance. 2D flexible and light materials with remarkable chemical and physical attributes such as acceptable conductivity, high surface metal diffusivity, hydrophilic surfaces, and mechanical strengths were introduced as potential options for battery electrodes. In present research, 2D orthorhombic di-boron di-nitride monolayer (o-B2N2) as a novel 2D boron nitride allotrope has been investigated. Systematically, various impacting factors like their electrochemical and electronic features (theoretical capacity, equilibrium voltage, binding strength, etc.) were investigated. It is noteworthy that specific capacity of K-ion batteries (KIBs) reaches 2347 mAh.g-1. In addition, the existence of o-B2N2 ring accelerates the diffusion of K-ions, and diffusion barriers are 0.14 eV. Mean open circuit voltage (OCV) and low diffusion barrier of o-B2N2 monolayer guarantee long service life and fast charging/discharging for practical purposes. Based on results, monolayer o-B2N2 is proper as a high-performance negative electrode material in KIBs.

Uncovering the remarkable electrochemical performance of B2N2 monolayer as a promising candidate for Mg-ion batteries

Nowadays, owing to their potential applications in next-generation self-powered electronic devices, such as energy-harvesting smart garments from body movements and roll-up displays, electrochemical energy storages are enjoying considerable interest. Nonetheless, the development of such technologies has been hindered due to the rarity of high-efficacy electrodes with specific electrochemical performance. Amongst prospective electrodes, researchers have investigated 2D flexible and lightweight materials which have unique physiochemical attributes such as high conductance, high surface metal diffusivity, a hydrophilic surface and mechanical strength. Within this piece of research, a 2D orthorhombic di-boron di-nitride monolayer (o-B2N2ML), which is a boron nitride allotrope, was investigated. Moreover, several determining electronic chemical factors were investigated, such as theoretical capacity, equilibrium voltage and binding strength. Interestingly, the Mg-ion battery had a specific capacity of up to 1125 mAh.g−1. Also, the diffusion of Mg-ions was accelerated due to the presence of a o-B2N2 ring with a diffusion barrier (DB) of 0.26 eV. The low OCV and the low DB of the o-B2N2ML demonstrate that it can be used for practical purposes with long service life and fast rates of charge and discharge. The results also indicated the possible use of the o-B2N2ML as an anode material with high efficiency in MIBs.

Capture of novel sp hybridized Z-BN by compressing boron nitride nanotubes with small diameter

Experimental synthesis of new sp3 hybridized carbon/boron nitride structures remains challenging despite that numerous sp3 structures have been proposed in theory. Here, we showed that compressed multi-walled boron nitride nanotubes (MWBNNTs) and boron nitride peapods (C60@BNNTs) with small diameters could transform into a new sp3 hybridized boron nitride allotrope (Z-BN). This strategy is considered from the topological transition point of view in boron nitride nanotubes upon compression. Due to the increased curvature in compressed small-diameter MWBNNTs, the uncommon 4- and 8-membered rings in Z-BN could be more favorably formed. And the irreversible tube collapse is proved to be a critical factor for the capture of the formed Z-BN, because of the competition between the resilience of tube before collapse and the stress limitation for the lattice stabilization of Z-BN upon decompression. In this case, Z-BN starts to form above 19.0 GPa, which is fully reversible below 45 GPa and finally becomes quenchable at 93.5 GPa. This collapse-induced capture of the high-pressure phase could also be extended to other tubular materials for quenching novel sp3 structures.

Multifunctional two-dimensional graphene-like boron nitride allotrope of g-B3N5: A competitor to g-BN?

The challenge in materials science is to meet the functional requirements in various aspects, where multifunctional materials can greatly expand the scope of applications. Compounds formed by atoms of boron (B) and nitrogen (N) provide a superior platform for exploring multifunctional materials. However, previous studies mainly focused on three-dimensional due to the controversial stability of two-dimensional (2D) structures. Herein, we designed a multifunctional 2D graphene-like boron nitride material with a buckling structure, namely g-B3N5. The stability is comprehensively proved from the aspects of mechanical, thermal, dynamic, and energetic behaviours. Furthermore, we systematically explored its mechanics, electronics, thermal, and optical properties, respectively. Excellent performances are found in g-B3N5, i.e, negative Poisson's ratio, ultra-wide band gap (4.32 eV), low thermal conductivity (21.08 W/mK), and highly tunable photon absorption peak by strain engineering. The multifunctional performance can bring new vitality to the field of BN-phase semiconductors as a strong competitor of g-BN.

Revealing the superlative electrochemical properties of o-B2N2 monolayer in Lithium/Sodium-ion batteries

Promising flexible electrochemical energy storage systems (EESSs) are currently drawing considerable attention for their tremendous prospective end-use in portable self-powered electronic devices, including roll-up displays, and “smart” garments outfitted with piezoelectric patches to harvest energy from body movement. However, the lack of suitable battery electrodes that provides a specific electrochemical performance has made further development of these technologies challenging. Two-dimensional (2D) lightweight and flexible materials with outstanding physical and chemical properties, including mechanical strengths, hydrophilic surfaces, high surface metal diffusivity, and good conductivity, have been identified as a potential prospect for battery electrodes. In this study, taking a new 2D boron nitride allotrope, namely 2D orthorhombic diboron dinitride monolayer (o-B2N2) as representatives, we systematically explored several influencing factors, including electronic, mechanical, and their electrochemical properties (e.g., binding strength, ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, electrical conductivity, excellent ionic mobility, low equilibrium voltage with excellent stability, good flexibility, and extremely superior theoretical capacity, up to 8.7 times higher than that of widely commercialized graphite (3239.74 mAh g−1 Vs 372 mAh g−1) in case of Li-ion batteries and 2159.83 mAh g−1 in case of Na-ion batteries, indicating that the new predicted 2D o-B2N2 monolayer possess the capability to be ideal flexible anode materials for Lithium and Sodium-ion battery. Our finding provides valuable insights for experimental explorations of flexible anode candidates based on 2D o-B2N2 monolayer.

Primitive and O-Functionalized R-Graphyne-like BN Sheet: Candidates for SO2 Sensor with High Sensitivity and Selectivity at Room Temperature

In recent years, the successful production of various boron nitride allotropes has raised exciting prospects for 2D materials in the nano device area. Herein, two novel two-dimensional boron nitrid...

Ab initiocalculations of carbon and boron nitride allotropes and their structural phase transitions using periodic coupled cluster theory

We present an ab-initio study of boron nitride as well as carbon allotropes. Their relative thermodynamic stabilities and structural phase transitions from low- to high-density phases are investigated. Pressure-temperature phase diagrams are calculated and compared to experimental findings. The calculations are performed using quantum chemical wavefunction based as well as density functional theories. Our findings reveal that predicted energy differences often depend significantly on the choice of the employed method. Comparison between calculated and experimental results allows for benchmarking the accuracy of various levels of theory. The produced results show that quantum chemical wavefunction based theories allow for achieving systematically improvable estimates. We find that on the level of coupled cluster theories the low- and high-density phases of boron nitride become thermodynamically degenerate at 0 K. This is in agreement with recent experimental findings, indicating that cubic boron nitride is not the thermodynamically stable allotrope at ambient conditions. Furthermore we employ the calculated results to assess transition probabilities from graphitic low-density to diamond-like high-density phases in an approximate manner. We conclude that the stacking order of the parent graphitic material is crucial for the possible formation of meta-stable wurtzite boron nitride and hexagonal carbon diamond also known as lonsdaleite.

High-throughput screening for superhard carbon and boron nitride allotropes with superior stiffness and strength

In search of intrinsically superhard materials with superior stiffness and strength, we performed a comprehensive high-throughput hunting on hundreds of carbon and BN allotropes based on energetic and mechanical criteria. Our results suggest that at ambient pressure, an approximate linear relationship exists between the ideal strengths and elastic moduli in two allotrope regions with high elastic moduli, while no carbon (BN) allotrope can possess both superior stiffness and strength than diamond (c-BN). With further consideration of pressure induced stiffening and strengthening, it is interestingly found that the strength enhancement shows distinct characteristic trend, resulting in some intriguing ultra-stiffening and strengthening phenomena. In particular, a superdense carbon allotrope termed as tI12-C was unexpectedly discovered to possess superior stiffness and strength than diamond under high pressure. Electronic structure analysis indicates that an increasing charge accumulation appearing in tI12-C under pressure is responsible for its ultra-stiffening and strengthening phenomena, differing from the appearance of abnormal charge depletions and the accompanied metallization in diamond under applied strain. These findings provide a fundamental basis for screening the novel superhard carbon and BN allotropes based on mechanical criteria, and highlight the importance to understand the effect of strain tunable electronic structure on mechanical response of materials.

Single-Photon Emitters in Boron Nitride Nanococoons.

Quantum emitters in two-dimensional hexagonal boron nitride (hBN) are attractive for a variety of quantum and photonic technologies because they combine ultra-bright, room-temperature single-photon emission with an atomically thin crystal. However, the emitter's prominence is hindered by large, strain-induced wavelength shifts. We report the discovery of a visible-wavelength, single-photon emitter (SPE) in a zero-dimensional boron nitride allotrope (the boron nitride nanococoon, BNNC) that retains the excellent optical characteristics of few-layer hBN while possessing an emission line variation that is lower by a factor of 5 than the hBN emitter. We determined the emission source to be the nanometer-size BNNC through the cross-correlation of optical confocal microscopy with high-resolution scanning and transmission electron microscopy. Altogether, this discovery enlivens color centers in BN materials and, because of the BN nanococoon's size, opens new and exciting opportunities in nanophotonics, quantum information, biological imaging, and nanoscale sensing.

Electronic and mechanic properties of trigonal boron nitride by first-principles calculations

A new boron nitride allotrope with 6 atoms in a unit cell termed as trigonal BN (TBN), which belongs to P3121 space group, is theoretically investigated. Electronic structures, mechanic properties, phonon spectra and other properties were calculated by using first-principles based on density functional theory (DFT). The elastic constants reveal that TBN is mechanically stable. Furthermore, phonon dispersion indicates that TBN is dynamically stable. The calculated bulk modulus and shear modulus of TBN are 323 and 342 GPa, respectively. The calculated Young's modulus are Ex = Ey = 760 GPa, Ez = 959 GPa, indicating that TBN is a super-hard and brittle material. The universal anisotropy index, which is only 0.296, shows its weak anisotropy. Band structure states clearly that TBN is an indirect semiconductor with a band gap of 3.87 eV. The valence bands are mainly composed of N 2p states, and the conduction bands are mainly contributed by B 2p states. Simulated X-ray diffraction patterns (XRD) and Raman spectra were also provided for future experimental characterizations. Due to its band gap and super-hard properties, TBN may possess potential in super-hard, optical and electronic applications.

Hard three-dimensional BN framework with one-dimensional metallicity

Carbon can be metal, semiconductor or insulator depending on its structures, and its conductivity can be one-dimensional (1D), 2D, and 3D correspondingly. Boron Nitride (BN) is isoelectronic to carbon, but one prominent difference between the two systems is their electronic properties. For many years, the synthesized and predicted BN allotropes were always insulators, irrespective of their structures. In this paper, with the help of structures searching based on first-principles calculations, a sp2/sp3-hybridized metallic monoclinic 3D BN (M-BN) structure is proposed. M-BN can be viewed as puckered hexagonal-BN (h-BN) layers bucked by partial sp3 BN bonds. The electronic property analysis revealed that the metallicity of M-BN is attributed to the delocalized 2p electrons of the sp2 B and N atoms. The metallic B atoms and N atoms are aligns in two arrays along a 1D axial direction, resulting in the unusual 1D dual-threaded conduction in 3D M-BN structure. The enthalpy calculation have revealed that M-BN is the most energetically favorable structure among the predicted metallic BN structures so far, and it might be obtained via compressing layered h-BN precursor theoretically. Due to the 3D strong framework, M-BN has an estimated Vickers Hardness of 33.7 GPa, indicating it is a potential hard material with novel 1D conduction.

Novel 3D metallic boron nitride containing only sp2 bonds

As the closest isoelectronic analogue of carbon, boron nitride (BN) shares a similar structure with carbon from 1D nanotubes, 2D nanosheets, and 3D diamond structures. However, most BN structures are insulators, which limits their application. In this work, under the inspiration of the sp2 hybridized carbon honeycomb, we propose a hexagonal phase of BN consisting of only sp2 bonds, which exhibits intriguingly intrinsic metallicity. First-principles calculations confirm that this phase is both thermally and dynamically stable. Moreover, the calculations on the band structure, partial density states and electron localization function suggest that the metallic behavior is attributable to the delocalized B-2p electrons, leading to second-neighbor interaction between the pz states of sp2-bonded B atoms in adjacent layers. Our findings not only enrich the BN allotrope family with 3D structures but also stimulate further experimental interest in applications of metallic BN in electronic devices.

New two-dimensional boron nitride allotropes with attractive electronic and optical properties

Using first principles calculations, structural, electronic and optical properties of five new 2D boron nitride (BN) allotropes have been studied. The results exhibit that the cohesive energy for all these five new allotrope is positive such as all these systems are stable; therefore, it is possible to synthesize these structures in experiments. It is found that the band gap of all new 2D BN allotropes is smaller than the h-BN sheet. In our calculations the dielectric tensor is derived within the random phase approximation (RPA). Specifically, the dielectric function, refraction index and the loss function, of the 2D BN allotropes are calculated for both parallel and perpendicular electric field polarizations. The results show that the optical spectra are anisotropic along these two polarizations. The results obtained from our calculations are beneficial to practical applications of these 2D BN allotropes in optoelectronics and electronics.

First-principles study of the crystal structures and physical properties of H18-BN and Rh6-BN

As the analog of carbon allotropes, new three-dimensional (3D) boron nitride (BN) allotropes have attracted much attention of researchers due to their great importance in fundamental sciences and wide practical applications. Here, based on first-principles density-functional theory calculations, we predict two new stable BN allotropes: One is H18-BN with the P6¯m2 (D3h1) symmetry containing eighteen atoms in the hexagonal unit cell and the other is Rh6-BN with the R3¯m (C3v5) symmetry containing six atoms in the rhombohedral primitive unit cell. The dynamic stabilities of the two structures are examined through the phonon spectrum analysis as well as molecular dynamics simulations, whereas the mechanical properties are analyzed by elastic constants, bulk modulus and shear modulus. From the analysis of the enthalpy evolution with respect to pressure, we find that h-BN can be transformed into either H18-BN or RH6-BN structure under a higher pressure of ∼15 GPa. We also find that both the H18-BN and Rh6-BN allotropes are brittle materials with indirect band gaps of 2.31 and 4.48 eV, respectively. The simulated XRD spectra provide detailed structural information of H18-BN and Rh6-BN for future experimental examinations. Our findings not only greatly enrich the existing structural family of 3D-BN materials but also stimulate further experiments.

Electronic and pseudomagnetic properties of hybrid carbon/boron-nitride nanomaterials via ab-initio calculations and elasticity theory

Low dimensional materials such as Boron Nitride nanotube (BNNT) and graphene are attractive for demonstrating several fundamental physical properties and development of novel technologies in nano/micro-scale devices. Although various 3D carbon-based architectures are reported via covalent connection of carbon allotropes, the introduction of analogous 3D hybrid carbon/BN allotropes and determining their exquisite junction-induced properties remain elusive. Here, we focus on mono- and double-layer hybrid graphene/BNNT and graphene/carbon nanotubes (CNT) architectures and explore their diverse junction configuration-induced electronic and pseudomagnetic properties via ab-initio calculations and elasticity theory. By introducing heptagonal and octagonal rings in the junctions, we find that the mismatch between the defected graphene and the BNNT/CNT diameters creates a bond strain at the junction, thus inducing a gauge field and pseudomagnetic field, which decay exponentially along the radial distance of the junction. Furthermore, our analysis of the band structures and density of states in hybrid double-layer architectures demonstrate that there exists a flat band and band dispersion near the Fermi level of graphene/CNT junctions, a feature not present in the graphene/BNNT junction due to the intrinsic wide band gap of BNNT. Finally, our size-effect study shows that while the band gap energy of heptagonal graphene/CNT junction and octagonal graphene/BNNT junctions is sensitive to the nanotube length, this is not the case for octagonal graphene/CNT junctions due to the less perturbation of the electronic states of the valence bond (VB) in the octagonal graphene/CNT junctions. Together, these findings have important implications on science-based engineering of numerous hybrid carbon and boron nitride allotropes while significantly broadening the spectrum of strategies for fabricating new hybrid nanomaterials through covalent connection of dissimilar low-dimensional materials.

A first-principles study on three-dimensional covalently-bonded hexagonal boron nitride nanoribbons

We studied three-dimensional honeycomb-structure boron nitride (BN) allotrope using first-principles calculations and the tight-binding method. Interconnected by sp3-bonding at the vertices, hexagonal BN nanoribbons construct highly-porous, covalently-bonded hexagonal BN nanoribbons (CBBNs). We investigated the structural and mechanical properties of CBBNs with various sizes, compared with those of carbon and other BN allotropes. The mechanical and thermal stabilities are also checked. Our calculations show that, despite the high porosity and low mass density, CBBNs are stable and mechanically hard materials as cubic BN. Moreover, our calculated results suggest that CBBNs can be regarded as a binary alloy of sp2- and sp3-bonded BNs following the Vegard's rule in average bond lengths and bulk moduli. Calculated band structures show that the band gap of CBBNs has similar variation upon increasing size as BN nanoribbons and is also limited by the second-neighbor interaction between the pz states of sp2-bonded atoms in adjacent nanoribbons.

A novel two-dimensional material B2S3and its structural implication to new carbon and boron nitride allotropes

We propose a single layer of B2S3as a new potential 2D material, conceived directly from its existing layered 3D crystal. New 2D BN and graphene allotropes are constructed from B2S3.

Effect of Interstitial Si on Different Boron Nitride Allotropes

Boron nitride (BN) is a very interesting material, being isoelectronic with diamond. It can form the following allotropes; hexagonal (h-BN), cubic (c-BN), wurtzitic (w-BN), and rhombohedral (r-BN). However, there are severe problems with the syntheses of some of these crystalline phases, especially using chemical vapor deposition (CVD) techniques. The underlying reasons for these growth difficulties are of largest importance to investigate more in detail. For each of these crystalline phases, the thin film surface reactivity is one factor that has a major influence on both growth and surface properties. The surface reactivity of specifically the B and N surface sites on these crystalline phases has therefore here been studied by performing first-principle density functional theory (DFT) calculations under periodic conditions. The following surfaces were studied: c-BN (100), h-BN (001), w-BN (100), and r-BN (001). The adsorption energy for different surface-terminating species (H, F, and Cl) has been taken as a measure of surface site reactivity. Since experimental studies have shown that Si contamination will improve the possibility for growth of r-BN, the effect of this dopant has also been considered in the present work. The results indicate that the surface reactivities for nonterminated N-sites are more pronounced for the situations with an otherwise completely covered surface by H species (compared to F and Cl). In fact, this was the situation for all BN allotropes (c-, h-, w-, and r-BN). The surface reactivities for nonterminated B-sites showed the same behavior for the w- and r-BN phases. For the c- and h-BN surfaces, a nonterminated B surface site on an otherwise H-terminated surface is, however, slightly less reactive compared to the corresponding F-terminated surface. In addition, there were extreme problems to terminate the various surfaces with Cl species. Furthermore, the existence of interstitial Si dopants did only show a positive effect for the reactivity of a bare B-site on the h- vs r-BN surface (on an otherwise H-terminated surface). However, the calculated stabilization energy showed that it is not possible to Si dope the h-BN surface lattice. Hence, it was only for r-BN that interstitial positioning of Si was found possible, and that also gave a positive effect on the surface reactivity.