Structures of indium oxide nanobelts

Indium oxide nanobelts of growth directions of [100] type (majority) and [120] type (minor) have been found. The two types of nanobelts have the top and bottom surfaces being (001), while the [100] type nanobelts have side surfaces of (010) and a rectangular cross-section, and the [120] type nanobelts have a parallelogram cross-section. The nanobelts have a perfect crystal structure without the presence of line or planar defects.     

Electrical properties of Cu-O monolayers intercalated into crystalline graphite

Electrical properties of Cu-O monolayers intercalated into crystalline graphite have been studied at microwave frequencies (up to 1 GHz) in the temperature range 80–400 K. As the temperature increases above 300 K, the resistance of the starting graphite samples increases because of oxygen desorption. Heating a sample containing intercalated Cu-O layers results in a transition from the metallic to the semiconducting (or insulating) state in the 95–130 K interval. At T=8 K, the samples exhibit microwave absorption typical of superconductors (this effect is not observed at T=260 K). Fiz. Tverd. Tela (St. Petersburg) 39, 97–100 (January 1997)     

Preparation and structural characterization of zwitterionic surfactant intercalated into NiZn-layered hydroxide salts

Three zwitterionic surfactants, dodecyl dimethyl carboxylbetaine (DCB), dodecyl dimethyl sulfobetaine (DSB) and N-dodecyl-β-aminoprpionate (DAP), intercalated into NiZn-layered hydroxide salts (NZL-DCB, NZL-DSB and NZL-DAP) were synthesized by the coprecipitation method. The effect of surfactant content, pH, temperature and time of hydrothermal treatment on preparation was investigated and discussed. The NZL-DCB, NZL-DSB and NZL-DAP were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry analysis and differential thermal analysis (TGA/DTA). The results showed that basal spacings of NZL-DCB, NZL-DSB and NZL-DAP were around 3.45, 3.68 and 3.94 nm, respectively. DCB, DSB and DAP probably form an overlapped bilayer in the gallery. TGA/DTA data indicated that NZL-DCB, NZL-DSB and NZL-DAP displayed three loss weight stages: loss of adsorbed and structural water, dehydroxylation of matrix and decomposition of nitrate ions, decomposition and combustion of surfactants. Furthermore, chemical analysis data, BET surface area and scanning electron microscopic (SEM) were also measured and analyzed.     

Structures and non-equilibrium dynamics in granular media

In granular media, dissipation leads to interesting phenomena like cluster formation in non-equilibrium dynamical states. As an example, the freely cooling system is examined concerning the energy decay and the cluster evolution with time. Furthermore, the probability distribution of the collision frequency is discussed. Uncorrelated events lead to a Poisson distribution for the collision frequencies in the homogeneous system, whereas cooperative phenomena can be related to a power-law decay of the collision probability per unit time. To cite this article: S. Luding, C. R. Physique 3 (2002) 153–161.     

Lattice dynamics of cupric oxide

By inelastic neutron scattering we have measured phonon dispersion curves of CuO in several directions. The phonon data are well reproduced by a 22 parameter rigid ion model. Various models with reduced numbers of fit parameters are described.     

Lattice dynamics of lithium oxide

Li₂O finds several important technological applications, as it is used in solid-state batteries, can be used as a blanket breeding material in nuclear fusion reactors, etc. Li₂O exhibits a fast ion phase, characterized by a thermally induced dynamic disorder in the anionic sub-lattice of Li⁺, at elevated temperatures around 1200 K. We have carried out lattice-dynamical calculations of Li₂O using a shell model in the quasi-harmonic approximation. The calculated phonon frequencies are in excellent agreement with the reported inelastic neutron scattering data. Thermal expansion, specific heat, elastic constants and equation of state have also been calculated which are in good agreement with the available experimental data.     

Crystal dynamics of magnesium oxide

Phonon dispersion curves, for MgO, have been calculated, for the first time, in the framework of the modified three body force shell model (TSM), assuming both the positive and negative ions to be polarizable. The results are in good agreement with the inelastic neutron scattering measurements and are somewhat better than our earlier one-ion polarizable TSM calculations. It has been possible to conclude that a revised set of values of the elastic constants which are relatively larger, is essentially responsible to lead to a better set of model parameters and hence of the phonon frequencies.     

Jump diffusion coefficient of different cations intercalated into amorphous WO3

This work shows how the combination of quasi-equilibrium (chronopotentiometry) and kinetical measurements (electrochemical impedance) is able to extract ionic mobility values like the jump diffusion coefficient D_J. Results are presented on the jump diffusion coefficient variation with composition of several cations (Li⁺, Na⁺, and K⁺) intercalated into electron beam evaporation-prepared a-WO₃ thin films. D_J exhibits higher values for the smallest ion (Li⁺), and decreases as the ion size enlarges. In all cases D_J shows lower values for high intercalation levels. It is noted that the type of cation rather influences transport mechanisms than equilibrium properties (insertion thermodynamics). The energy barrier of ion hopping is analyzed in light of available microscopic diffusion models and theoretical simulations.     

Lattice dynamics of calcium oxide

The effect of the electronic extension on the electrostatic potential was first taken into account functionally by Birman. We have applied his model to the lattice dynamics of CaO, where the degree of the electronic extension w was defined and determined with the use of the electronic charge density distribution obtained from analysis of X-ray data. Our treatment shown here not only gives a physically meaningful model including the feature of the electronic extension, but also involves essentially the same very simple process as the conventional point-charge model but with fewer adjustable parameters. Good reproduction of calculated phonon dispersion curves was obtained by taking into account the electronic extension, although the degree of the electronic extension, w, used to fit the curve was a little larger than that derived from the observed data owing to the first rough approximation for the potential energy arising from the electronic extension.     

Spectroscopic evidence of co-insertion of carbon atoms into Li intercalated layered compounds

Co-insertion of solvent into layered compounds intercalated with lithium has been evidenced by Raman scattering measurements. The penetration of solvated species into the host is observed in samples prepared by an electrochemical technique as well as by direct chemical reaction in n-butyl lithium. The co-insertion is evidenced by the appearance of peaks in the spectral range 1200–1800 cm^–1 which are attributed to vibrations due to carbon atoms.     

Peculiar diffusion behavior of AlCl_4 intercalated in graphite from nanosecond-long molecular dynamics simulations

The diffusion property of the intercalated species in the graphite materials is at the heart of the rate performance of graphite-based metal-ion secondary battery. Here we study the diffusion process of a AlCl_4 molecule within graphite — a key component of a recently reported aluminum ion battery with excellent performance — via molecular dynamics(MD) simulations. Both ab-initio MD(AIMD) and semiempirical tight-binding MD simulations show that the diffusion process of the intercalated AlCl_4 molecule becomes rather inhomogeneous, when the simulation time exceeds approximately 100 picoseconds. Specifically, during its migration in between graphene layers, the intercalated AlCl_4 molecule may become stagnant occasionally, and then recovers its normal(fast) diffusion behavior after halting for a while. When this phenomenon occurs, the linear relationship of the mean squared displacement(MSD) versus the duration time is not fulfilled. We interpret this peculiar behavior as a manifestation of inadequate sampling of rare event(the stagnation of the molecule), which does not yet appear in short-time MD simulations. We further check the influence of strains present in graphite intercalated compounds(GIC) on the diffusion properties of AlCl_4, and find that their presence in general slows down the diffusion of the intercalated molecule, and is detrimental to the rate performance of the GIC-based battery.     

Molecular dynamics simulations of lanthanum oxide surfaces

Classical molecular dynamics was used to investigate the equilibrium state of the surface region of as-grown La₂O₃. It is currently thought that bulk and epitaxial thin film La₂O₃ surfaces exhibit amorphous structures in the as-prepared state that yield bulk crystal states upon postdeposition annealing. The focus of the study is to determine if the as-prepared surface region of La₂O₃ is purely amorphous as indicated from prior experimental results. Using simulation cells sufficiently large to accommodate the formation of defects, phase segregation, compositional migration, and site defects, our results show that crystalline phases are evident from simulated X-ray diffraction patterns. Although the phase of these crystallites is unresolved, we suggest that combinations of distorted hexagonal, cubic, and nonstoichiometric phases are formed in the as-prepared state prior to annealing. These crystallites likely serve as nucleation site for long-range ordered crystal growth upon annealing.     

Decays of Z Bosons into Triple-Quark and Double-Quark Structures

This paper presents a mechanism of decay of elementary particles, which has been developed based on a new approach. The results obtained may be of interest to experimenters engaged in the decay of Z ⁰ bosons. Schemes and modes of the structural decay of gamma structures, one of which is the Z ⁰ boson, are given. Analysis of the schemes and modes of the structural decay has shown that the decays of the product triple-quark particles (products of the decay of a Z ⁰ boson into triple-quark particles) result in the occurrence of a new mode of decay – the decay of one triple-quark particle into three triple-quark particles. According to the proposed mechanism of the decay of particles, an electron, a muon, a triton, and a gamma photon are particles consisting of a quark–antiquark pair and having a spin equal to unity.     

电场诱导氧化石墨烯的极化动力学特性研究

本文通过外加电场改变氧化石墨烯团簇分子的共振能量,利用激光激发氧化石墨烯产生的共振荧光特性测量氧化石墨烯在电场作用下的极化动力学特性. 发现存在外加电场使得荧光共振峰的半高全宽趋于饱和的时间特性,而不同的氧化石墨烯团簇分子的荧光共振峰的暂态特性同时反映了电场对氧化石墨烯产生定向极化和变形极化的动力学特性. 关键词： 氧化石墨烯 团簇分子 电场 极化动力学     

Molecular dynamics studies of the interaction between water and oxide surfaces

The water-surface interaction is a research target of great importance for a broad spectrum of technological applications and fundamental scientific disciplines. In the present study, a comparative analysis is performed to clarify the structural and diffusion properties of water on a number of oxide surfaces. Based on the molecular dynamics (MD) simulation method, the water-surface interaction mechanism was investigated for the oxide materials TiO₂ (anatase), Al₂O₃ (corundum), and Fe₂O₃ (hematite). A comparison of the water-TiO₂ interaction with the water-Al₂O₃ and water-Fe₂O₃ systems demonstrates the specificity of the adsorption and layer formation on the atomic/molecular level scale. The obtained MD analysis data point to a considerable enhancement of water-TiO₂ surface adsorption and a relatively high density distribution profile near the surface. The novel data on water structure and diffusion on oxide surfaces are discussed from the point of view of possible material innovation and design.     

Structures, energetics, and dynamics of helium adsorbed on isolated fullerene ions

Helium adsorbed on C(60)(+) and C(70)(+) exhibits phenomena akin to helium on graphite. Mass spectra suggest that commensurate layers form when all carbon hexagons and pentagons are occupied by one He each, but that the solvation shell does not close until 60 He atoms are adsorbed on C(60)(+), or 62 on C(70)(+). Molecular dynamics simulations of C(60)He(n)(+) at 4 K show that the commensurate phase is solid. Helium added to C(60)He(32)(+) will displace some atoms from pentagonal sites, leading to coexistence of a registered layer of immobile atoms interlaced with a nonregistered layer of mobile atoms.     

小碳团簇结构的从头算分子动力学模拟

引入第一原理密度泛函理论, 即赝势密度泛函在实空间的有限差分方法和朗之万分子动力学退火技术, 对碳团簇Cn(n=2-8)的基态结构进行了理论计算, 所得结果与其他作者的计算结果及实验数据吻合较好.