Narrow Results

Structural and electronic properties of perovskite KCaX₃ (X = F and Cl) compounds are investigated using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in the Wien2k code. The exchange-correlation potential is treated by the generalized gradient approximation within the scheme of Perdew, Burke and Ernzerhof (GGA-PBE). Based on these calculations, it has been concluded that KCaX₃ compounds have indirect energy band-gap (Γ-R). Moreover, the theoretical investigation which has been carried out on the highly hydrostatic pressure dependence of the KCaX₃ electronic properties revealed a linear relationship between both the hydrostatic pressure and the energy band-gap. In addition, the electronic and bonding properties of the band structure, density of states (DOS) and electron charge density have been calculated and presented. Besides that, the dielectric function, refractive index and extinction coefficient are calculated. The origin of some of the peaks in the optical spectra is discussed in terms of the calculated electronic structure. Finally, the calculated structural properties are found to agree well with the available experimental and theoretical data.

In this paper, the influence of laser irradiance on the plasma characteristics of a silver target is investigated in relation to one another. A Q-switched nanosecond Nd:YAG laser with the fundamental harmonic wavelength (1064 nm) and an irradiance ranging from $4.82\times 10^8$ W/cm² to $6.21\times 10^8$ W/cm² was used to irradiate these matrices. The irradiance was measured at atmospheric pressure. Temperature of the plasma and the electron density were calculated for different laser intensities of silver based on their oxidation states. The Boltzmann plot and the Stark broadening technique were used to compute the properties of the plasma ($T_e$ and $n_e)$. Based on the findings, it is clear that the temperature of the electrons in the Ag plasma does not increase linearly with increasing laser irradiation. These variations in the temperatures of the electrons in those matrices are brought on by matrix effects. On the other hand, an increase in laser irradiance was shown to cause an increase in electron density, which resulted in a widening of the line profiles associated to electron density.

Theoretical isotropic (spherically symmetric) Compton profiles (ICP) have been calculated for many particle systems' He, Li, Be and B atoms in their ground states. Our calculations were performed using Roothan–Hartree–Fock (RHF) wave function, HF wave function of Thakkar and re-optimized HF wave function of Clementi–Roetti, taking into account the impulse approximation. The theoretical analysis included a decomposition of the various intra and inter shells and their contributions in the total ICP. A high momentum region of up to 4 a.u. was investigated and a non-negligible tail was observed in all ICP curves. The existence of a high momentum tail was mainly due to the electron–electron interaction. The ICP for the He atom has been compared with the available experimental data and it is found that the ICP values agree very well with them. A few low order radial momentum expectation values 〈pⁿ〉 and the total energy for these atomic systems have also been calculated and compared with their counterparts' wave functions.

For simple plasma diagnostics for laser-induced plasma (LIP) under the condition of optically thin, taking the Cu I spectral lines produced by the laser-induced copper plasma, we investigate a simple method for temperature and electron density diagnostics, and we obtain the plasma temperature which has 10⁴ K order of magnitude and the averaged electron density is $3.8\times 10^{18}{\mathrm{\text{cm}}}^{-3}$, which are in agreement with that obtained by other methods. This investigation will be significant for spectral diagnostics for LIP.

In this work, we use a method based on the concept of particle confinement time $({\tau }_p)$ uniqueness to calculate the electron density and temperature in ohmically heated, edge plasma of the Hefei tokamak-7. Here, with the help of the data taken from Johnson and Hinnov’s table, we have done an extensive work to find electron densities and temperatures that satisfy the ${\tau }_p$ uniqueness to evaluate the temporal evolution of electron density $(n_e)$ and temperature $(T_e)$. The results are in good agreement as measured from the Langmuir probe array in previous works.

The electronic structures and optical properties of pure ZnO and IIIA group elements Al-, Ga- and In-doped wurtzite ZnO are studied by using first-principles plane density of states pseudopotential method based on the density functional theory. Considering the difference between doped and undoped situation, the band structure, total/partial wave density and dielectric function, refractive index, reflectivity, absorption spectrum and loss function are investigated. The results show that all the three doped elements transform the pure ZnO into $n$-type direct band gap semiconductor materials, and the band gap becomes smaller and smaller with the enhancement of the gold property of the doped elements. In addition, it is found by comparison that Al doping has the highest conductivity. In the visible light region, Ga-doped ZnO has a good transmittance and is an ideal transparent conductive material. In-doped ZnO has higher absorption rate and emission rate, and has a great application prospect in ultraviolet protection. The results have a positive reference value for IIIA main group elements in ZnO doping design.

Based on Pauling's nature of chemical bond, the valence electron structures of TiN and FeAl have been constructed, and the relative electron density differences (REDD) between the low index plane of TiN and FeAl, respectively, have been calculated. [110] _FeAl//[110]_TiN crystallography orientation has been set up from the minimization of the electron density difference across the interface. From the viewpoint of improving the mechanical properties of composites, the formation of such structures must been engineered in the fabrication processing.

Intermetallic matrix composites reinforced with ceramic particles such as TiC have received increasing attention in recent years due to the combined potential of ceramics and intermetallics to give a desirable balance of properties. But an understanding of some experimental results presented elsewhere has remained elusive. In this communication, interface valence electron structure of TiC–NiAl composites was set up on the basis of Pauling's nature of the chemical bond, and valence electron density ρ of different atomic states TiC and NiAl composites in various planes was determined. From the viewpoint of biphase interface electron density continuing, the corresponding experimental phenomena are explained.

Three different metal–organic frameworks (MOFs), specifically Mn₂(dobdc)(DMF)₄ (H₂dobdc=[2,5-dihydroxyterephthalic acid]; compound (1), Mn₅(btac)₄(μ₃-OH)₂(EtOH)₂⋅DMF⋅3EtOH⋅3H₂O (H₂btac=[benzotriaole-5-carboxylicacid]; compound (2), and Mn₃(2,6-ndc)₃⋅4DMF (H₂ndc=[2,6-naphthalenedicarbo-xylic acid]; compound (3), have been synthesized, the channels of which are lined with coordinatively unsaturated Mn^II centers. The adsorption of O₂ in these MOFs has been measured using a gravimetric method at different temperatures (-78°C, -5°C, and 25°C) at a pressure of 1 bar. Gas adsorption isotherms of compounds 1 and 2 at 298 K indicated that they bind O₂ by chemisorption at low pressure, with capacities of 1.2 wt.% and 2.14 wt.%, respectively, for the first cycle, with reversible oxygen binding for compound 1 and partially irreversible oxidation for compound 2. However, compound 3 binds O₂ by physisorption, with a capacity of just 0.21 wt.%. This difference between the three compounds stems from the different coordination environments of the respective Mn^II centers, which give rise to differences in electron density. The results suggest that there must be an optimal electron density around the exposed Mn^II center for partial charge transfer from this center to the bound O₂ molecule; if the electron density is too high or too low, reversible chemisorption of O₂ is not favored.

The periodic nature of the myelin sheath makes it well-suited for examination of its molecular organization by diffraction techniques. Diffraction provides a means not only of monitoring the separation between membranes, but also of analyzing the forces and interactions between them. The diffraction technique is nonperturbing, and is uniquely suited to analyzing myelin structure and stability in physiologically intact, unfixed tissue. In principle, changes in structure can be followed in real time during physiological events or experimental treatments. The correlation of results from diffraction with results from electron microscopy and chemical analysis has led to a description of the distribution of lipid, protein, and water in the membrane array and to the localization of specific proteins and lipids within the membrane. Such studies are providing the foundation for understanding the molecular roles of particular myelin lipids and of specific myelin proteins — both native and mutated — in membrane–membrane adhesion and myelin stability.

The cylindrical geometric space defect is a new example of geometric defects, which proved useful in the description of defects in solid state physics. Here we present a short qualitative exposition of the application of cylindric geometric defect to multiwall nanotubes.