Query: BC6N

title: Highly enhanced NH3 sensing performance of BC6N monolayer with single vacancy and Stone Wales defects: A DFT study
abstract: Searching for suitable NH3 sensing materials has important scientific significance and application value. Using DFT calculations, the adsorption behaviors, electronic, gas sensing, and optical properties of NH3 and other common molecules on the BC6N monolayer without and with single vacancy (MV) and Stone Wales (SW) defects were investigated to fully exploit the possibilities of the BC6N monolayer as a NH3 gas sensor. Our results showed that the pure BC6N monolayer has bad gas sensing performance for NH3 detection. The BC6N monolayer with MVC, MVN, MVB, and rippled SW defects are all dynamically stable. The studies on adsorption behaviors (adsorption energy, geometric structures, and adsorption mode) charge transfer, electron density difference, electronic and optical properties indicate that the BC6N monolayer with MVC, MVN, and rippled SW defects is promising candidates for NH3 sensors, indicating the introduction of monovacancies (MVC, MVN, and rippled SW) in BC6N monolayer can enhance strongly the NH3 sensing performance.

title: First principles studies of superhard BC6N phases with unexpected 1D metallicity
abstract: Three novel sp2 sp3 hybridized BC6N phases with a sandwich structure, including a type of orthorhombic BC6N (o BC6N) and two types of tetragonal BC6N (t BC6N 1 and t BC6N 2) are investigated through first principles calculations. The structural stabilities are confirmed by the calculated elastic constants and phonon dispersions. Calculated electronic band structures, density of states (DOS) and partial DOS show that the o BC6N, t BC6N 1, and t BC6N 2 crystals may possess the metallicity with the conducting electrons from the p orbits of sp2 hybridized C atoms. Calculations of electron orbits indicate that the electrons in o BC6N and t BC6N 1 structures can conduct through the p bonds along the orientation parallel to the [1 0 0] and [0 1 0] directions in different layers. Moreover, the electrons in t BC6N 2 structure can conduct along the orientation parallel to the [1 1 0] and 1 1 0] directions in different layers. The behavior of the linear electron conductivity in the layer and vertical direction of conduction between the adjacent layers imply that the three kinds of crystals have potential applications in the field effect devices. Calculation results using the semi empirical microscopic model show that o BC6N, t BC6N 1, and t BC6N 2 are potential superhard materials with Vickers hardness of 52.4, 45.3, and 40.1 GPa, respectively.

title: Ultrahigh thermal conductivity in hexagonal BC6N An efficient material for nanoscale thermal management A first principles study
abstract: Engineering materials with high thermal conductivity are of fundamental interest for efficiently dissipating heat in micro/nanoelectronics. Using first principles computations we report an ultra high thermal conductivity of 2090 Wm 1K 1 (1395 Wm 1K 1) for hexagonal pure (natural) BC6N(h BC6N) This value is among the highest thermal conductivities known after diamond and cubic boron arsenide. This ultra high lattice thermal conductivity (k) is mainly attributed with high phonon group velocities of both acoustic and optical phonons arising from strong C C and B N bonds as well as the light atomic mass of the constituent elements such as boron (B) carbon (C) and nitrogen (N) We also report size dependent thermal conductivity of h BC6N nanostructures by including boundary scattering. At room temperature (300 K) and at nanoscale length (L) of 100 nm, a high k value of 175 Wm 1K 1 is observed (higher than the bulk k value of silicon) Optical phonons with large group velocities are mainly responsible for this high thermal conductivity in h BC6N nanostructures. High thermal conductivity of h BC6N makes it a candidate material for heat dissipation in micro/nano thermal management applications.

title: Ultrahigh thermal conductivity and strength in direct gap semiconducting graphene like BC6N: A first principles and classical investigation
abstract: In recent years, graphene like boron carbide and carbon nitride nanosheets have attracted remarkable attentions, owing to their semiconducting electronic nature and outstanding mechanical and heat transport properties. Graphene like BC6N is an experimentally realized layered material and most recently has been the focus of numerous theoretical studies. Interestingly, the most stable form of BC6N monolayer remains unexplored and limited information are known concerning its intrinsic physical properties. Herein, on the basis of density functional theory (DFT) calculations we confirm that the most stable form of BC6N nanosheet shows a rectangular unitcell, in accordance with an overlooked experimental finding. We found that BC6N monolayer is a semiconductor with 1.19 eV HSE06 based direct gap and yields anisotropic and excellent absorption of visible light. First principles results highlight that BC6N nanosheet exhibits anisotropic and ultrahigh tensile strength and lattice thermal conductivity, outperforming all other fabricated 2D semiconductors. We moreover develop classical molecular dynamic models for the evaluation of heat transport and mechanical properties of BC6N nanomembranes. The presented results in this work not only shed light on the most stable configuration of BC6N nanosheet, but also confirm its outstandingly appealing electronic, optical, heat conduction and mechanical properties, extremely motivating for further theoretical and experimental endeavors.

title: Estudo de Propriedades Eletronicas e Estruturais de Nanoestruturas BC6N via Calculos de Primeiros Principios
abstract: Um novo campo da fisica da materia condensada, tanto experimental quanto relacionado a simulacoes computacionais, surgiu com a descoberta dos nanotubos de carbono, os quais apresentam propriedades fisico quimicas unicas, tais como grande dureza e flexibilidade. Alem das promissoras propriedades mecanicas, estudos teoricos e experimentais mostraram que dependendo do diametro e quiralidade o tubo e metalico ou semicondutor. Tal comportamento pode ser qualitativamente explicado em termos da estrutura de banda e dos vetores de onda discretos permitidos pelas condicoes de contorno nos tubos de carbono. Similarmente, os compostos III V podem ser encontrados em estruturas hexagonais e tubulares microscopicas. O material III V com maior similaridade ao carbono e o nitreto de boro, que como o carbono, e encontrado em estruturas sp2 e sp3. Assim, podemos criar combinacoes estequiometricas do tipo BxCyNz. Devido a ionicidade do nitreto de boro e ao seu grande gap de energia ~4.9 eV) tubos desse material apresentam maior uniformidade nas propriedades eletronicas quando comparados ao carbono e seus tubos serao sempre semicondutores (quase) unidimensionais. Isso pode ser tecnologicamente vantajoso porque amostras contendo tubos de tamanhos e estruturas diferentes podem ser crescidos com propriedades predeterminadas. Neste trabalho fizemos a substituicao parcial de carbono por atomos de boro e nitrogenio, levando nos a formacao de compostos ternarios BC6N de grandes diametros. Tais composicoes permitem a obtencao de estruturas de bandas com gap de energia intermediario entre os apresentados pelo grafite e pelo nitreto de boro. Entao empregamos um metodo de primeiros principios para realizacao dos calculos de estrutura eletronica, para o quais utilizamos o codigo computacional SIESTA, que realiza calculos autoconsistentes. O formalismo do codigo SIESTA e fundamentado na teoria do funcional da densidade, com o termo de exchange correlacao tratado atraves da aproximacao da densidade local ou da aproximacao do gradiente generalizado, com o uso de pseudopotenciais de norma conservada e de um conjunto de bases, obtidas da combinacao linear de orbitais atomicos.Mais especificamente, estudamos, atraves de calculos ab initio, a estabilidade das estruturas BC6N atraves da determinacao da energia de formacao, energia de coesao e energia de strain. Alem disso, investigamos as propriedades eletronicas de tais estruturas, na ausencia de defeitos. Em relacao as propriedades estruturais nossos resultados mostram que os tubos assumem uma forma elipsoidal com diferentes excentricidades, as quais dependem do diametro do tubo. A analise energetica mostra que tubos de grande diametro sao mais estaveis e a analise eletronica mostra que os nanotubos sao semicondutores com gaps direto de energia, variando entre ~0,3 ate ~1,1) eV.

title: Electronic structure and intercalation chemistry of graphite like layered material with a composition of BC6N
abstract: Electronic structure of graphite like layered material with a composition of BC 6 N, which was prepared at 1470 K by the chemical vapor deposition (CVD) method, was investigated by X ray emission spectroscopy (XES) and X ray absorption spectroscopy (XAS) using synchrotron radiation. The X ray emission and absorption spectra in the B K C K and N K regions of BC 6 N were considerably different from those of h BN and graphite, probably because of a hybridization for orbitals of boron, carbon and nitrogen existing in the same layer of BC 6 N. Angle resolved XES and XAS indicated the structural orientation of the BC 6 N film, which was also observed by X ray diffraction (XRD) analysis. Density of states (DOS) in the occupied 2p orbitals calculated by the discrete variational (DV) X a method for one (type A) of structural models which was considered on the basis of the CVD reaction, fitted with the measured X ray emission spectra of BC 6 N. The intercalation phenomena of alkali metal into BC 6 N are similar to those of graphite, which is probably due to the band overlap and the relatively large DOS of the unoccupied p orbital of the material.

title: Ground state properties and hardness of high density BC6N phases originating from diamond structure
abstract: We report two possible metastable high density BC6N phases originating from the diamond structure. The ground state properties of the BC6N phases are calculated using first principles density functional methods and the Vickers hardness is estimated using a semiempirical microscopic model. The calculated results show that two BC6N phases are semiconductors with Vickers hardness about 79 80GPa, indicating that the zinc blende like BC6N compounds are superhard material and have larger hardness than cubic BC2N and cubic boron nitride.

title: Intercalation chemistry of graphite like layered material BC6N for anode of Li ion battery
abstract: Films with an approximate composition of BC6N were prepared by the reaction of acrylonitrile with boron trichloride (mole ratio=2:1) at 1470 2070 K under atmospheric pressure. The films obtained at 1470 and 2070 K had graphite like layered structure whose interlayer spaces were 0.339 and 0.342 nm, respectively. Rapid chemical intercalation of Li into the BC6N prepared at 2070 K was observed in Li C 10 H 8 2 MeTHF solution, resulting in formation of the first stage intercalation compound with an interlayer space (d spacing) of 0.365 nm. The BC6N prepared at 1470 K performed electrochemical charge/discharge cycles similar to those of graphite in 1 M LiPF6/EC+DEC solution. The first stage compound of LiXBC6N, which was prepared by the electrochemical method, had a d spacing of 0.355 nm smaller than that of LiC6 (0.370 nm) The small expansion ratio in d spacing [4.7%(0.355 0.339)/0.339}x100] could be one of the advantages of the BC6N material for the usage as Li ion battery anode.

title: Synthesis of graphite like material of composition BC6N by CVD at high temperature

title: Preparation and electronic state of graphite like layered material BC6N
abstract: The material with a composition of BC6N was obtained by the reaction of acrylonitrile with boron trichloride mole ratio =2 1) at 1500 1800degC under atmospheric pressure. The films obtained at 1500 and 1800degC had graphite like layered structure whose interlayer spacings (nano space) were 0.350 and 0.342 nm, respectively. The band gap of BC6N was estimated to be larger than that of graphite by the comparison of their reduction and oxidation potentials. The potential change during the electrochemical intercalation of lithium into BC6N electrode was also quite different from that into graphite. These results suggest that BC6N has a novel nano space between the layers and is a promising material as a new semiconductor and a unique host material.