Raman spectroscopy has become an essential technique to characterize and investigate graphene and many other two-dimensional materials. However, there still lacks consensus on the Raman signature and phonon dispersion of atomically thin boron nitride (BN), which has many unique properties distinct from graphene. Such a knowledge gap greatly affects the understanding of basic physical and chemical properties of atomically thin BN as well as the use of Raman spectroscopy to study these nanomaterials. Here, we use both experiment and simulation to reveal the intrinsic Raman signature of monolayer and few-layer BN. We find experimentally that atomically thin BN without interaction with substrate has a G band frequency similar to that of bulk hexagonal BN, but strain induced by substrate can cause pronounced Raman shifts. This is in excellent agreement with our first-principles density functional theory (DFT) calculations at two levels of theory, including van der Waals dispersion forces (opt-vdW) and a fractional of the exact exchange from Hartree-Fock (HF) theory through hybrid HSE06 functional. Both calculations demonstrate that the intrinsic E2g mode of BN does not depend sensibly on the number of layers. Our simulations also suggest the importance of the exact exchange mixing parameter in calculating the vibrational modes in BN, as it determines the fraction of HF exchange included in the DFT calculations.
In an attempt to understand why catalytic methods for the growth of boron nitride nanotubes work much worse than for their carbon counterparts, we use first-principles calculations to study the energetics of elemental reactions forming N2, B2 and BN molecules on an iron catalyst. We observe that in the case of these small molecules, the catalytic activity is hindered by the formation of B2 on the iron surface. We also observe that the local morphology of a step edge present in our nanoparticle model stabilizes the boron nitride molecule with respect to B2 due to the ability of the step edge to…
Imaging and spectroscopy performed in a low-voltage scanning transmission electron microscope (LV-STEM) are used to characterize the structure and chemical properties of boron-terminated tetravacancies in hexagonal boron nitride (h-BN). We confirm earlier theoretical predictions about the structure of these defects and identify new features in the electron energy-loss spectra (EELS) of B atoms using high resolution chemical maps, highlighting differences between these areas and pristine sample regions. We correlate our experimental data with calculations which help explain our observations.
The effect of doping of cubic boron nitride with beryllium, silicon, sulfur and magnesium on the lattice parameters, electrical conductivity and EPR spectra has been studied. It is established that the degree of doping increases significantly in the case of crystallization of cubic boron nitride from BN solutions in supercritical ammonia at 3.9-4.2 GPa and 1100°C in comparison with the conventional synthesis from melts of the Mg-B-N system at 4.2 GPa and 1400°C. Doping with silicon and beryllium results in semiconductor properties of cubic boron nitride.
Cathodoluminescence imaging and spectroscopy experiments on a single bamboo-like boron nitride nanotube are reported. Imaging experiments show that the luminescence is located all along the nanotube. Spectroscopy experiments point out the important role of dimensionality in this one dimensional object.
A comparison between experimental and theoretical electron Energy Loss Near Edge Structure (ELNES) of B and N K-edges in cubic boron nitride is presented. The electron energy loss spectra of cubic boron nitride particles were measured using a scanning transmission electron microscope. The theoretical calculation of the ELNES was performed within the framework of density functional theory including single particle core-hole effects. It is found that experimental and calculated ELNES of both the B and N K-edges in cubic boron nitride show excellent agreement.
Recently hybridized monolayers consisting of hexagonal boron nitride (h-BN) phases inside graphene layer have been synthesized and shown to be an effective way of opening band gap in graphene monolayers [1]. In this letter, we report an ab initio density functional theory (DFT)- based study of h-BN domain size effect on the elastic properties of graphene/boron nitride hybrid monolayers (h-BNC). We found both inplane stiffness and longitudinal sound velocity of h-BNC linearly decrease with h-BN concentration.
We report on the measurement of the effective radial modulus of multiwalled Boron Nitride nanotubes with external radii in the range 3.7 to 36 nm and number of layers in between 5 and 48. These Boron Nitride nanotubes are radially much stiffer than previously reported thinner and smaller Boron Nitride nanotubes. Here, we show the key role of the morphology of the nanotubes in determining their radial rigidity, in particular we find that the external and internal radii, R_ext and R_int, have a stronger influence on the radial modulus than the NT's thickness, t. We find that the effective radial…
Atomically thin boron nitride (BN) is an important two-dimensional (2D) nanomaterial, with many properties distinct from graphene. In this feature article, these unique properties and associated applications often not possible from graphene are outlined. The article starts with characterization and identification of atomically thin BN. It is followed by demonstrating their strong oxidation resistance at high temperatures and applications in protecting metals from oxidation and corrosion. As flat insulators, BN nanosheets are ideal dielectric substrates for surface enhanced Raman spectroscopy (…
Nanostructure and mechanical properties of bulk nanocristalline cubic boron nitride have been studied by transmission electron microscopy, and micro- and nanoindentation. The obtained data on hardness, elastic properties and fracture toughness clearly indicate that nano-cBN belongs to a family of advanced ultra-hard materials.
Graphene nanoribbons are prepared inside boron nitride nanotubes by liquid phase encapsulation and subsequent annealing of 1,2,4-trichlorobenzene. The product is imaged with high resolution transmission electron microscopy, and characterized by optical absorption and Raman spectroscopy. Carbon-containing material is detected inside the boron nitride nanotubes with energy-dispersive x-ray spectroscopy (EDS) and scanning transmission electron microscopy (STEM). The observed structures twist under the electron beam and the characteristic features of nanoribbons appear in the Raman spectra.
Despite a recent flurry of experimental and simulation studies, an accurate estimate of the interaction strength of water molecules with hexagonal boron nitride is lacking. Here we report quantum Monte Carlo results for the adsorption of a water monomer on a periodic hexagonal boron nitride sheet, which yield a water monomer interaction energy of -84 +/- 5 meV. We use the results to evaluate the performance of several widely used density functional theory (DFT) exchange correlation functionals, and find that they all deviate substantially. Differences in interaction energies between different …
We demonstrate the fabrication of individual nanopores in hexagonal boron nitride (hBN) with atomically precise control of the pore size. Previous methods of pore production in other 2D materials create pores of irregular geometry with imprecise diameters. By taking advantage of the preferential growth of boron vacancies in hBN under electron beam irradiation, we are able to observe the pore growth via transmission electron microscopy, and terminate the process when the pore has reached its desired size. Careful control of beam conditions allows us to nucleate and grow individual triangular an…
Uniaxial tensile properties of hexagonal boron nitride nanoribbons and dependence of these properties on temperature, strain rate, and the inclusion of vacancy defects have been explored with molecular dynamics simulations using Tersoff potential. The ultimate tensile strength of pristine hexagonal boron nitride nanoribbon of 26 nm x 5 nm with armchair chirality is found to be 100.5 GPa. The ultimate tensile strength and strain have been found decreasing with increasing the temperature while an opposite trend has been observed for increasing the strain rate. Furthermore, the vacancy defects re…
Using combination of Density Functional Theory and Monte Carlo simulation, we study the phase stability and electronic properties of two dimensional hexagonal composites of boron nitride and graphene, with a goal to uncover the role of the interface geometry formed between the two. Our study highlights that preferential creation of extended armchair interfaces may facilitate formation of solid solution of boron nitride and graphene within a certain temperature range. We further find that for band-gap engineering, armchair interfaces or patchy interfaces with mixed geometry are most suitable. E…
The defect-mediated hexagonal boron nitride (hBN) supercell display the visible optical spectra and electronic characteristics. The defects in the hBN supercell include the atomic vacancy, antisite, antisite vacancy, and substitution of a foreign atom for boron or nitrogen. The hBN supercell with VB, CB, and NB-VN has the high electron density of states across the Fermi level which indicates the high conductive electronic characteristics. The hBN with defects including atomic vacancy, antisite vacancy, and substitution of a foreign atom for boron or nitride exhibit the distinct spin-resolved o…
The phonon dispersion, density of states, Grüneisen parameters, and the lattice thermal conductivity of single- and multi-layered boron nitride were calculated using first-principles methods. For the bulk {\it h}-BN we also report the two-phonon density of states. We also present simple analytical solutions to the acoustic vibrational mode-dependent lattice thermal conductivity. Moreover, computations based on the elaborate Callaway-Klemens and the real space super cell methods are presented to calculate the sample length and temperature dependent lattice thermal conductivity of single- and mu…
Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent dielectric substrate for graphene, molybdenum disulfide and many other 2D nanomaterials based electronic and photonic devices. To optimize the performance of these 2D devices, it is essential to understand the dielectric screening properties of BN nanosheets as a function of the thickness. Here, electric force microscopy along with theoretical calculations based on both state-of-the-art first-principles calculations with van der Waals interactions under consideration and non-linear Thomas-Fermi theory models are used to…
The sputtering of hexagonal boron nitride due to low energy xenon ion bombardments occurs in various applications including fabrication of cubic boron nitride and erosion of Hall thruster channel walls. At low ion energies, accurate experimental characterization of sputter yields increases in difficulty due to the low yields involved. A molecular dynamics model is employed to simulate the sputtering process and to calculate sputter yields for ion energies ranging from 10 eV to 350 eV. The results are compared to experimental data and a semi-empirical expression developed by Bohdansky is found …
Ab initio calculations of the spontaneous polarization and piezoelectric properties of boron nitride nanotubes show that they are excellent piezoelectric systems with response values larger than those of piezoelectric polymers. The intrinsic chiral symmetry of the nanotubes induces an exact cancellation of the total spontaneous polarization in ideal, isolated nanotubes of arbitrary indices. Breaking of this symmetry by inter-tube interaction or elastic deformations induces spontaneous polarization comparable to those of wurtzite semiconductors.
In the present work we discuss based on extensive fully atomistic molecular dynamics simulations the dynamics of Neon atoms oscillating inside (5,5)single-walled carbon nanotubes (CNTs) and boron-nitride (BNNT) ones. Our results show that sustained high frequency oscillatory regimes are possible for a large range of temperatures. Our results also show that the general features of the oscillations are quite similar to CNT and BNNT, in contrast with some speculations in previous work literature about the importance of broken symmetry and chirality exhibited by BNNTs.
The dispersion of nitride and carbide ceramic particles in water is difficult, due to the absence of hydroxyl groups on their surface. Boron nitride is not an exception and despite its numerous applications, no effective dispersant has been identified so far. We demonstrate here the dispersion properties of two cellulose derivatives for hexagonal boron nitride powders, hydroxyl ethyl cellulose and methyl cellulose. The effect of particle sizes and cellulose concentration was investigated. The adsorption of cellulose onto the surface of the BN particles was confirmed by isotherm adsorption. Zet…
In this work we show, by means of a density functional theory formalism, that the simple physical contact between hydrogen terminated boron nitride surfaces gives rise to a metallic interface with free carries of opposite sign at each surface. A band gap can be induced by applying uniaxial pressure. The size of the band gap changes continuously from zero up to 4.4 eV with increasing pressure, which is understood in terms of the interaction between surface states. Due to the high thermal conductivity of cubic boron nitride and the coupling between band gap and applied pressure, such tunable ban…
Covalent functionalization is a way to tune the electrochemical properties of hexagonal boron nitride (h-BN) monolayers. The wide band gap insulator h-BN may become metallic conductor upon functionalization with strong oxidants, such as fluorosulfonyl radicals ($\cdot$OSO$_2$F), as known since 1978 [N. Bartlett et al., J. Chem. Soc. Chem. Comm. {\bf 5}, 200 (1978)], with electrical conductivity of 1.5 S/cm [C. Shen et al., J. Solid State Chem. {\bf 147}, 74 (1999)] that greatly surpasses commercial cathode material Li$_{x}$CoO$_{2}$ while retaining excellent ionic conductivity. Functionalized …
Topological insulators hold great potential for efficient information processing and storage. Using density functional theory calculations, we predict that a honeycomb lead monolayer can be stabilized on the Al2O3 (0001) substrate and becomes topologically non-trivial with a sizeable band gap (~0.27 eV). Furthermore, we propose to use hexagonal boron-nitride (h-BN) monolayer as a protection for the topological states of Pb/Al2O3 and Sn/Al2O3. Our findings suggest new possibilities for designing and protecting two-dimensional TIs for practical applications.
High pressure Raman experiments on Boron Nitride multi-walled nanotubes show that the intensity of the vibrational mode at ~ 1367 cm-1 vanishes at ~ 12 GPa and it does not recover under decompression. In comparison, the high pressure Raman experiments on hexagonal Boron Nitride show a clear signature of a phase transition from hexagonal to wurtzite at ~ 13 GPa which is reversible on decompression. These results are contrasted with the pressure behavior of carbon nanotubes and graphite.
Carbon nanoscrolls (CNSs) are structures formed by rolling up graphene layers into a papyruslike shape. CNNs have been experimentally produced by different groups. Boron nitride nanoscrolls (BNNSs) are similar structures using boron nitride instead of graphene layers. In this work we report molecular mechanics and molecular dynamics results for the structural and dynamical aspects of BNNS formation. Similarly to CNS, BNNS formation is dominated by two major energy contributions, the increase in the elastic energy and the energetic gain due to van der Waals interactions of the overlapping surfa…
The current rechargeable battery technologies have a failure in their performance at high pressure and temperature. In this article, we have brought theoretical insights on using boron nitride flakes as a protecting layer for a lithium-ion battery device and extended its application for a spin-dependent photon emission device. Hence, the electronic properties of pristine and lithium-doped hydrogen-edged boron nitride flakes have been studied by the first principle density functional theory calculations. In this study, we have discussed the stability, adsorption energies, bond lengths, electron…
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 benchmarki…
The excitonic recombinations in hexagonal boron nitride (hBN) are investigated with spatially resolved cathodoluminescence spectroscopy in the UV range. Cathodoluminescence images of an individual hBN crystallite reveals that the 215 nm free excitonic line is quite homogeneously emitted along the crystallite whereas the 220 nm and 227 nm excitonic emissions are located in specific regions of the crystallite. Transmission electron microscopy images show that these regions contain a high density of crystalline defects. This suggests that both the 220 nm and 227 nm emissions are produced by the r…
The interlayer sliding energy landscape of hexagonal boron nitride (h-BN) is investigated via a van der Waals corrected density functional theory approach. It is found that the main role of the van der Waals forces is to "anchor" the layers at a fixed distance, whereas the electrostatic forces dictate the optimal stacking mode and the interlayer sliding energy. A nearly free-sliding path is identified, along which bandgap modulations of ~0.6 eV are obtained. We propose a simple geometrical model that quantifies the registry matching between the layers and captures the essence of the corrugated…
The stability of atomic intercalated boron nitride K4 crystal structures, XBN (X=H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ga, Ge, As, Se, Br, Rb or Sr) is evaluated by the geometric optimization and frozen phonon calculations based on the first principles calculations. NaBN, MgBN, GaBN, FBN and ClBN are found to be stable. NaBN, GaBN, FBN and ClBN are metallic, whereas MgBN is semiconducting.
We find, with the use of first-principles calculations, that a single-atom-thick boron-nitride (BN) sheet exhibits an unusual nonlinear electromechanical effect: it becomes macroscopically polarized when bent out-of-plane. The direction of the induced polarization is in the plane of the film and it depends non-analitically on the corrugation wave vector k. The magnitude of the polarization can reach very high values in spite of being at least quadratic in atomic displacements due to BN sheets being able to tolerate large mechanical strains. The discovered effect can find many applications, in …
The growth of nanotube films on various substrates and surfaces is vital for applications in nanoscale functional devices. We report a simple and versatile boron (B) ink painting method that enables high-density boron nitride nanotube (BNNT) films with any desired pattern to be grown on, and firmly attached to, different surfaces. In the method, special B ink is first painted, sprayed or inkjet printed at desired location with required pattern, and then the ink layer is annealed in a nitrogen-containing atmosphere to form BNNT film. The B ink is a liquid mixture of ball-milled B particles, met…
Spin-polarized density functional theory calculations have been performed on armchair graphene quantum dots and boron-nitride quantum dots (A-G/BN-QDs) and the effect of carbon/boron-nitride substitution on the electronic properties of these A-G/BN-QDs has been investigated. As a first step to consider more realistic quantum dots, quantum dots which are a combination of zigzag QDs and armchair QDs have been considered. Effect of substitution on these hybrid quantum dots has been explored for both GQDs and BNQDs and such results have been compared and contrasted with the results of substituted …
Hexagonal boron nitride is a wide bandgap semiconductor with a very high thermal and chemical stability often used in devices operating under extreme conditions. The growth of high-purity crystals has recently revealed the potential of this material for deep ultraviolet emission, with an intense emission around 215 nm. In the last few years, hexagonal boron nitride has been raising even more attention with the emergence of two-dimensional atomic crystals and Van der Waals heterostructures, initiated with the discovery of graphene. Despite this growing interest and a seemingly simple structure,…
Quantum emitters in layered hexagonal boron nitride (hBN) have recently attracted a great attention as promising single photon sources. In this work, we demonstrate resonant excitation of a single defect center in hBN, one of the most important prerequisites for employment of optical sources in quantum information application. We observe spectral linewidths of hBN emitter narrower than 1 GHz while the emitter experiences spectral diffusion. Temporal photoluminescence measurements reveals an average spectral diffusion time of around 100 ms. On-resonance photon antibunching measurement is also r…
Hexagonal boron nitride (h-BN) is a layered two-dimensional material with properties that make it promising as a dielectric in various applications. We report the growth of h-BN films on Ni foils from elemental B and N using molecular beam epitaxy. The presence of crystalline h-BN over the entire substrate is confirmed by Raman spectroscopy. Atomic force microscopy is used to examine the morphology and continuity of the synthesized films. A scanning electron microscopy study of films obtained using shorter depositions offers insight into the nucleation and growth behavior of h-BN on the Ni sub…
The minimum thermal conductance versus supercell size ($d_{s}$) is revealed in graphene and boron nitride superlattice with $d_{s}$ far below the phonon mean free path. The minimum value is reached at a constant ratio of $d_{s}/L\approx 5%$, where $L$ is the total length of the superlattice; thus the minimum point of $d_{s}$ depends on $L$. The phenomenon is attributed to the localization property and the number of confined modes in the superlattice. With the increase of $d_{s}$, the localization of the confined mode is enhanced while the number of confined modes decreases, which directly resu…
We use a tight binding approach and density functional theory calculations to study the band structure of graphene/hexagonal boron nitride bilayer system in the most stable configuration. We show that an electric field applied in the direction perpendicular to the layers significantly modifies the electronic structure of the whole system, including shifts, anticrossing and other deformations of bands, which can allow to control the value of the energy gap. It is shown that band structure of biased system may be tailored for specific requirements of nanoelectronics applications. The carriers' m…
We investigate key electrical properties of monolayer graphene assembled by chemical-vapor-deposition (CVD) as impacted by supporting substrate material. Graphene field-effect transistors (GFETs) were fabricated with carbon channel placing directly on hexagonal boron nitride (h-BN) and SiO2, respectively. Small-signal transconductance (gm) and effective carrier mobility (μeff) are improved by 8.5 and 4 times on h-BN, respectively, as compared with that on SiO2. Compared with GFET with exfoliated graphene on SiO2, gm and μeff measured from device with CVD graphene on h-BN substrate exhibits com…
Spin defects in foils of hexagonal boron nitride are an attractive platform for magnetic field imaging, since the probe can be placed in close proximity to the target. However, as a III-V material the electron spin coherence is limited by the nuclear spin environment, with spin echo coherence time of $\sim100~\mathrm{ns}$ at room temperature accessible magnetic fields. We use a strong continuous microwave drive with a modulation in order to stabilize a Rabi oscillation, extending the coherence time up to $\sim4~\mathrm{μs}$, which is close to the 10-$\mathrm{μs}$ electron spin lifetime in our …
The possibility of modification of the local properties of hexagonal boron nitride (h-BN) by laser irradiation is investigated. Investigations conducted using both Raman spectroscopy and electrostatic force microscopy were performed. Laser light induced modifications are found to cause no structural changes. However, they have impact on Raman spectra and local charge state of the material. They are also shown to be stable in time and during electrical grounding of the sample. The mechanism of photoionization of deep defects present in h-BN is proposed to explain the observed phenomenon. The di…
The Vickers hardness of polycrystalline γ-B was measured using a diamond indentation method. The elastic properties of polycrystalline γ-B (B=213.9 GPa, G=227.2 GPa, and E=503.3 GPa) were determined using ultrasonic measurement at ambient condition. Under the loading force up to 20 N, our test gave an average Vickers hardness in the asymptotic-hardness region of 30.3 GPa. The average fracture toughness was measured as 4.1MPa m1/2. Additionally, We also measured the hardness and elastic properties of polycrystalline β-B and PcBN for comparison. The hardness and elastic properties for polycrysta…
A new interpretation of the optical and energy-loss spectra of hexagonal boron nitride is provided based on first-principle calculations. We show that both spectra cannot be explained by independent-particle transitions but are strongly dominated by excitonic effects. The lowest direct and indirect gaps are much larger than previously reported. The direct gap amounts to 6.8 eV. The first absorption peak at 6.1 eV is due to an exciton with a binding energy of 0.7 eV. We show that this strongly bound Frenkel exciton is also responsible for the low frequency shoulder of the pi plasmon in the ener…
We have studied zig-zag boron nitride (BN) nanotubes doped with the Ni hexagonal-closepacked nanowire. The doped BN nanotubes are ferromagnetic metals with substantial magnetism. Some special magnetic properties resulting from the interaction between the Ni nanowire and BN nanotubes are found. The Ni doped BN(9,0) nanotube shows semi-half-metallic behavior, which could become half-metallic after doping electrons more than 1.4 e/unit cell. The intrinsic halfmetallic behavior could be achieved by two dierent ways: one is coating the Ni nanowire with a smaller BN nanotube, i.e., BN(8,0), the othe…
Single layer hexagonal boron nitride is produced on 2 inch Pt(111)/sapphire wafers. The growth with borazine vapour deposition at process temperatures between 1000 and 1300 K is in-situ investigated by photoelectron yield measurements. The growth kinetics is slower at higher temperatures and follows a tanh$^2$ law which better fits for higher temperatures. The crystal-quality of h-BN/Pt(111) is inferred from scanning low energy electron diffraction (x-y LEED). The data indicate a strong dependence of the epitaxy on the growth temperature. The dominant structure is an aligned coincidence lattic…
Electronic properties of the graphene layer sandwiched between two hexagonal boron nitride sheets have been studied using the first-principles calculations and the minimal tight-binding model. It is shown that for the ABC-stacked structure in the absence of external field the bands are linear in the vicinity of the Dirac points as in the case of single-layer graphene. For certain atomic configuration, the electric field effect allows opening of a band gap of over 230 meV. We believe that this mechanism of energy gap tuning could significantly improve the characteristics of graphene-based field…
Atomically thin boron nitride (BN) nanosheets are important two-dimensional nanomaterials with many unique properties distinct from those of graphene, but the investigation of their mechanical properties still greatly lacks. Here we report that high-quality single-crystalline mono- and few-layer BN nanosheets are one of the strongest electrically insulating materials. More intriguingly, few-layer BN shows mechanical behaviors quite different from those of few-layer graphene under indentation. In striking contrast to graphene, whose strength decreases by more than 30% when the number of layers …
We report non-resonant x-ray Raman scattering (XRS) measurements from hexagonal boron nitride for transferred momentum from 2 to 9 $\mathrmÅ^{-1}$ along directions both in and out of the basal plane. A symmetry-based argument, together with real-space full multiple scattering calculations of the projected density of states in the spherical harmonics basis, reveals that a strong pre-edge feature is a dominantly $Y_{10}$-type Frenkel exciton with no other \textit{s}-, \textit{p}-, or \textit{d}- components. This conclusion is supported by a second, independent calculation of the \textbf{q}-depen…
A first-principles investigation of the electronic properties of boron nitride nanoribbons (BNNRs) having either armchair or zigzag shaped edges passivated by hydrogen with widths up to 10 nm is presented. Band gaps of armchair BNNRs exhibit family-dependent oscillations as the width increases and, for ribbons wider than 3 nm, converge to a constant value that is 0.02 eV smaller than the bulk band gap of a boron nitride sheet owing to the existence of very weak edge states. The band gap of zigzag BNNRs monotonically decreases and converges to a gap that is 0.7 eV smaller than the bulk gap due …
The stacking orders in layered hexagonal boron nitride bulk and bilayers are studied using high-level ab initio theory (local second-order Moller-Plesset perturbation theory, LMP2). Our results show that both electrostatic and London dispersion interactions are responsible for interlayer distance and stacking order, with AA' being the most stable one. The minimum energy sliding path includes only the AA' high-symmetry stacking, and the energy barrier is 3.4 meV per atom for the bilayer. State-of-the-art Density-functionals with and without London dispersion correction fail to correctly describ…
Possible crystalline modifications of chemical compounds at low temperatures correspond to local minima of the energy landscape. Determining these minima via simulated annealing is one method for the prediction of crystal structures, where the number of atoms per unit cell is the only information used. It is demonstrated that this method can be applied to covalent systems, at the example of boron nitride, using ab initio energies in all stages of the optimization, i.e. both during the global search and the subsequent local optimization. Ten low lying structure candidates are presented, includi…
In this work, sintered polycrystalline cubic boron nitride (cBN) compacts, with titanium carbonitride (TiC0.7N0.3) and titanium nitride (TiN), respectively, as binders, were prepared at temperature of 1450°C and pressure of 5.5 GPa during 3 minutes, and the influence of binders on the plastic deformation of cBN powder due to the sintering process was experimentally investigated by X-ray diffraction (XRD) analysis. It was shown that the sintered compact with titanium carbonitride as a binder displays more intense plastic deformation of cBN grains than that with titanium nitride binder. This res…
We represent the results of quantum chemical calculations of boron nitride nanotubes intercalated by alkali and alkali-earth metall atoms and its ions. It was obtained that unpair spins were localized on seperated metal atoms. So we propose to construct the two-qubit cells on the basis of infilled boron nitride nanotubes for the quantum computer.
