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1.
Methods of molecular mechanics are used to calculate cluster structures of new carbon phases of 3D graphite. It is established
that 3D graphite polytypes differ by the structure of layers and order of their alternation, consist of sp
2 hybridized atoms, and have hexagonal unit cells. New carbon phases can be synthesized by polymerization and carbonization
of hydrocarbon molecules. 相似文献
2.
Carbon has always attracted attention due to its rich chemistry and the almost complementary properties of the natural phases graphite and diamond. While graphite is a highly anisotropic semi‐metal, diamond shows high hardness and thermal conductivity and is a wide‐gap insulator. With the discovery of graphene, fullerenes, and carbon nanotubes which resemble properties of the two crystalline phases, research on those and novel carbon materials emerged. Since carbon is forming different covalent bonds, there is a multitude of possibilities to create new structures by just combining sp, sp2, and sp3 bonded carbon. Here we report on the discovery of a new sp2 and sp3 bonded carbon structure which can be seen as a crossed graphene structure providing hybrid properties of graphene and diamond by means of an evolutionary algorithm.
3.
The elastic moduli and propagation velocities of elastic waves in 2D supracrystalline nanoallotropes of carbon have been calculated.
It has been shown that these velocities in sp
2 nanoallotropes are close to those in graphene and exceed the propagation velocities of elastic waves in single-crystal diamond
by a factor of 2. The propagation velocities of both longitudinal and transverse elastic waves in carbon 2D supracrystalline
sp
3 nanoallotropes are several times lower than those in sp
2 nanoallotropes. 相似文献
4.
This paper reviews progress that has been made in the use of Raman spectroscopy to study graphene and carbon nanotubes. These are two nanostructured forms of sp2 carbon materials that are of major current interest. These nanostructured materials have attracted particular attention because of their simplicity, small physical size and the exciting new science they have introduced. This review focuses on each of these materials systems individually and comparatively as prototype examples of nanostructured materials. In particular, this paper discusses the power of Raman spectroscopy as a probe and a characterization tool for sp2 carbon materials, with particular emphasis given to the field of photophysics. Some coverage is also given to the close relatives of these sp2 carbon materials, namely graphite, a three-dimensional (3D) material based on the AB stacking of individual graphene layers, and carbon nanoribbons, which are one-dimensional (1D) planar structures, where the width of the ribbon is on the nanometer length scale. Carbon nanoribbons differ from carbon nanotubes is that nanoribbons have edges, whereas nanotubes have terminations only at their two ends. 相似文献
5.
《Physics letters. A》2019,383(17):2093-2096
Covalent functionalization of graphene is recently developed from the formation of sp3 hybridized carbon atom (sp3-C) to the sp3 hybridized nitrogen (sp3-N) at the anchoring site. Here, we investigated the electronic structures and transport properties of the zigzag graphene nanoribbons functionalized by covalently bonding of p-aminophenol (p-AP) molecule. First principles results demonstrate that the formed sp3-N plays a vital role in determining the electronic structure and transport properties of the system, resulting in a halfmetallic characteristic with a perfect spin-filtering behavior (100%). Interestingly, the performance of the spin-filtering is find to be insensitive to the sub-structures of the molecule. Our findings reveal the importance of sp3-N and suggest a new mechanism for realizing high-performance spin-filtering devices with functionalized graphene. 相似文献
6.
基于密度泛函理论,采用了一种更为精确的交换相关泛函OLYP(OPTX+LYP),对密度范围从2.0到3.2 g/cm3的非晶碳进行结构建模. 模拟得到的5个碳网络结构无论从径向分布函数还是sp3含量都与实验符合得很好. 对非晶碳电子结构的研究表明费米能级附近的电子态密度主要是sp2碳原子的贡献. 随着密度的增加,sp3碳原子增加,费米能级附近的态密度越来越小. 小环结构增加了费米能级附近的电子态密度,缺陷态在费米能级形
关键词:
非晶碳
密度泛函理论
电子结构 相似文献
7.
8.
Molecular dynamic calculations are carried out for the (P, T) phase diagram of a covalent compound of cross-linked carbon single-wall nanotubes (SWNT) and for the structures and electronic spectra of the novel crystals of polymerized carbon nanotubes. It is shown that the transformation of covalently bonded nanotubes in a close-packed conducting structure cardinally modifies their electronic properties. The P-SWNT crystal becomes semiconducting and, upon complete transformation of sp 2-hybridized carbon atoms into sp 3-hybridized ones, it becomes an insulator. 相似文献
9.
10.
11.
B. Song Y. Yong J. Hou P. He 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(3):399-406
Density-functional theory with generalized gradient approximation for the exchange-correlation potential has been used to
calculate the structural and electronic properties of
Si
n
C
n
(n = 10–15) clusters. We find that the Si
n
C
n
clusters prefer cagelike structures. An extensive isomer search shows that the lowest-energy arrangements are those in which
the silicon atoms and the carbon atoms form two distinct subunits. It is found that the carbon atoms favor to form fullerene-like
structure due to the
sp
2-like bond. The silicon atoms are trying to cope with an unfavorable
sp
2 environment, but distorted tetrahedra still show up somewhere of the cagelike structures. On the basis of the lowest-energy
geometries obtained, the binding energy, HOMO–LUMO gap, Mulliken charge, ionization potential and electron affinity of the
clusters have been computed and analyzed. An electronic charge transfer from the Si-populated to the C-populated regions is
observed. 相似文献
12.
By applying nonequilibrium Green's functions (NEGF) in combination with density functional theory (DFT), the electronic transport properties of α-armchair graphyne nanoribbons (α-AGyNR) device are investigated, in which the left electrode is doped by Boron (B) atoms and the right electrode is doped by Nitrogen (N) atoms. B and N doping atoms that are substituted in SP and SP2 sites result in four devices named as A (sp–sp), B (sp2–sp2), C (sp2–sp) and D (sp–sp2). The current–voltage characteristics of these systems reveal that the proposed devices have a striking nonlinear feature that leads to formation of a p–n junction which results rectifying behavior. The results show that the rectification characteristics are strongly dependent on the site of doping atoms. In A and D devices the rectification ratio (RR) can reach to 103 in the bias region from 0.2 V to 0.6 V while in B and C devices the RR can be enlarged to 104 in the same bias region. Unlike the most of the previous proposed molecular rectifiers that are vertical hetero structures, the proposed rectifier in this work is in-plane or two dimensional structures. The results provide a new insight and a novel effective pathway for developing applicable high-performance Graphyne-based rectifiers. 相似文献
13.
Petr K. Sazonov Galina A. Artamkina Irina P. Beletskaya 《Journal of Physical Organic Chemistry》2008,21(3):198-206
Second order rate constants are reported for the reactions of metal carbonyl anions ([M(CO)nL]?) with several vinyl halides: PhCCl?C(CN)2, Z‐ and E‐Ph(CN)C?CHHal (Hal = Cl, Br) which follow the addition–elimination (AdNE) substitution mechanism. The obtained data show that the nucleophilic reactivity of [M(CO)nL]? anions towards vinyl halides increases in the same order as in aliphatic SN2 reactions, but much more steeply, by 14 orders of magnitude in the row log{ }: [CpFe(CO)2]? (~14), [Re(CO)5]? (7.8), [Mn(CO)5]? 2.1, [CpW(CO)3]? (0.7) > [CpMo(CO)3]? (0). A good correlation exists between nucleophilicities of [M(CO)nL]? anions towards vinyl (sp2‐carbon) and alkyl halides (sp3‐carbon) with slope 2.7. The reactivity of [M(CO)nL]? in a halogen–metal exchange process (with Z‐PhC(CN)?CHI) follows a similar ‘large’ scale as in the AdNE process. The nucleophilicity of [M(CO)nL]? anions correlates better with their one‐electron oxidation potentials (Eox) than with their basicity (pKa of [M(CO)nL]H). Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
14.
Hongliang Zhang Weidong Wu Chengshi Gong Wei Wang Zhibing He Jun Li Xin Ju Yongjian Tang Erqing Xie 《Applied Physics A: Materials Science & Processing》2010,98(4):895-900
Fe-doped hydrogenated amorphous carbon (a-C:H:Fe) films were deposited from a gas mixture of trans-2-butene/ferrocene/H2 by plasma enhanced metal organic chemical vapor deposition. X-ray photoelectron spectroscopy, Fourier transform infrared
spectra and Raman spectra were used to characterize the composition and the bonding structure of the a-C:H:Fe and a-C:H films.
Optical properties were investigated by the UV–visible spectroscopy and the photoluminescence (PL) spectra. The Fe-doped films
contain more aromatic structures and C=C bonds than the undoped films. The sp
2 carbon content and sp
2 clustering of the films increase, and aromatic-like rings’ structures become richer after Fe-doping. The Tauc optical gap
of the a-C:H:Fe films become narrower by 0.3 eV relative to the value of the a-C:H films. The PL peak shifts from 2.35 eV
of the a-C:H films to 1.95 eV of the a-C:H:Fe films, and the PL intensity of the a-C:H:Fe films is greatly enhanced. A deep
level emission peak around 2.04 eV of the a-C:H:Fe films is observed. 相似文献
15.
Structural variation in a synchrotron‐induced contamination layer (a‐C:H) deposited on a toroidal Au mirror surface 下载免费PDF全文
A carbon layer deposited on an optical component is the result of complex interactions between the optical surface, adsorbed hydrocarbons, photons and secondary electrons (photoelectrons generated on the surface of optical elements). In the present study a synchrotron‐induced contamination layer on a 340 mm × 60 mm Au‐coated toroidal mirror has been characterized. The contamination layer showed a strong variation in structural properties from the centre of the mirror to the edge region (along the long dimension of the mirror) due to the Gaussian distribution of the incident photon beam intensity/power on the mirror surface. Raman scattering measurements were carried out at 12 equidistant (25 mm) locations along the length of the mirror. The surface contamination layer that formed on the Au surface was observed to be hydrogenated amorphous carbon film in nature. The effects of the synchrotron beam intensity/power distribution on the structural properties of the contamination layer are discussed. The I(D)/I(G) ratio, cluster size and disordering were found to increase whereas the sp2:sp3 ratio, G peak position and H content decreased with photon dose. The structural parameters of the contamination layer in the central region were estimated (thickness ? 400 Å, roughness ? 60 Å, density ? 72% of bulk graphitic carbon density) by soft X‐ray reflectivity measurements. The amorphous nature of the layer in the central region was observed by grazing‐incidence X‐ray diffraction. 相似文献
16.
The diamond-like phases containing carbon atoms with the same degree of hybridization, which is close to sp
3, are classified. It is found that twenty such phases can exist, and ten of them are described for the first time. Molecular
mechanics and semi-empirical quantum-mechanical methods are used to calculate the geometrically optimized structures of diamond-like
phase clusters and to determine their structural parameters and properties, such as the density, the bulk modulus, and the
sublimation energy. The difference between the properties of the diamond-like phases and those of diamond is found to be determined
by the difference between the structures of these phases and diamond. 相似文献
17.
In this paper, we are investigating the Raman and photoluminescence properties of reduced graphene oxide sheets (rGO). Moreover,
graphene oxide (GO) sheets are synthesized using Hummer’s method and further reduced into graphene sheets using D-galactose.
Both GO and rGO are characterized by UV-vis spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS)
and Thermogravimetric (TGA) analysis. Raman analysis of rGO shows the restoration of graphitic domains in GO after reduction.
The photoluminescence of rGO showed emission in the UV region which is blue shifted along with luminescent quenching as compared
to GO. This blue shift and quenching in photoluminescence arises due to the newly formed crystalline sp2 clusters in rGO which created percolation pathways between the sp2 clusters already present. 相似文献
18.
Neeraj Dwivedi Sushil Kumar H.K. MalikGovind C.M.S. RauthanO.S. Panwar 《Applied Surface Science》2011,257(15):6804-6810
In the present work the correlation of electrical, optical and nano-mechanical properties of argon-diluted diamond-like carbon (Ar-DLC) thin films with sp3 and sp2 fractions of carbon have been explored. These Ar-DLC thin films have been deposited, under varying C2H2 gas pressures from 25 to 75 mTorr, by radio frequency-plasma enhanced chemical vapor deposition technique. X-ray photoelectron spectroscopy studies are performed to estimate the sp3 and sp2 fractions of carbon by deconvoluting C 1s core level spectra. Various electrical, optical and nano-mechanical parameters such as conductivity, I-V characteristics, optical band gap, stress, hardness, elastic modulus, plastic resistance parameter, elastic recovery and plastic deformation energy have been estimated and then correlated with calculated sp3 and sp2 fractions of carbon and sp3/sp2 ratios. Observed tremendous electrical, optical and nano-mechanical properties in Ar-DLC films deposited under high base pressure conditions made it a cost effective material for not only hard and protective coating applications but also for electronic and optoelectronic applications. 相似文献
19.
Correlations between the density, elastic properties, and hardness of the carbon phases prepared from C60 at a high pressure are studied. By varying the high pressure and temperature properly, one can obtain from C60 a broad class of ordered polymerized and disordered phases, for which the fraction of the sp2 and sp3 states, the characteristic dimensionality of the structure, the degree of covalent bonding, etc. can be varied successfully. 3D-bonded carbon structures are shown to exhibit a clearly pronounced correlation between the hardness or bulk modulus and the density, with these correlations also apparently applying to the carbon phases in a general case. At the same time, the mechanical characteristics of structures with a lower dimension covalent bonding are worse than those of 3D-bonded phases with similar values of the density. 相似文献
20.
以CF4,CH4和N2为源气体,利用射频等离子体增强化学气相沉积法,在不同功率下制备了含氮氟化类金刚石膜.用俄歇电子能谱、拉曼光谱、X射线光电子能谱和傅里叶变换红外光谱对薄膜的电子结构和化学键进行了表征,并结合高斯分峰拟合方法分析了薄膜中sp2,sp3结构比率.结果表明,制备的薄膜属于类金刚石结构,不同沉积功率下,薄膜内的sp2/sp3值在2.0—9.0之间,随着沉积功率的增加薄膜内sp2的相对含量增加.膜内主要有C—Fx(x=1,2),C—C,C=C和C≡N等化学键.沉积功率增加,C—C基团增加,膜内F的浓度降低,C—F基团减少,薄膜的关联加强,稳定性提高.
关键词:
含氮氟化类金刚石膜
sp结构
化学键结构
射频功率 相似文献