Synthesis, growth and characterization of a new derivative 4-ethoxy-N-methyl-4-stilbazolium besylate monohydrate single crystal

A new organic material 4-ethoxy-N-methyl-4-stilbazolium besylate monohydrate, a derivative in the stilbazolium family, known for efficient nonlinear optical materials, has been synthesized for the first time. Employing the slow evaporation technique, optically transparent good quality single crystals of size 15 mm×10 mm×5 mm were grown from methanol. The cell dimensions obtained by single crystal X-ray diffraction studies reveal that the crystal belongs to the monoclinic system. Functional groups of the grown crystal were identified from FTIR and NMR spectral analysis. UV−vis−NIR studies show that the crystal is transparent in the wavelength range 460-1100 nm. The thermal stability of the compound was determined by thermal analyses of the specimen.     

Structural and vibrational properties of Ca2FeH6 and Sr2RuH6

The structural and vibrational properties of the isostructural compounds Ca₂FeH₆ and Sr₂RuH₆ are determined by periodic DFT calculations and compared with their previously published experimental crystal structures as well as new experimental vibrational data. The analysis of the vibrational data is extended to the whole series of alkaline-earth iron and ruthenium hydrides A₂TH₆ (A=Mg, Ca, Sr; T=Fe, Ru) in order to identify correlations between selected frequencies and the T-H bond length. The bulk moduli of Ca₂FeH₆ and Sr₂RuH₆ have also been determined within DFT. Their calculated values prove to compare well with the experimental values reported for Mg₂FeH₆ and several other compounds of this structure.     

Modeling of lattice constant and their relations with ionic radii and electronegativity of constituting ions of A2XY6 cubic crystals (A=K, Cs, Rb, Tl; X=tetravalent cation, Y=F, Cl, Br, I)

In the present paper a new empirical model is proposed to describe and predict the lattice constants for a series of cubic crystals, all of which have the A₂XY₆ composition (A=K, Cs, Rb, Tl; X=tetravalent cation, Y=F, Cl, Br, I). The model is based on a thorough analysis of structural properties of 85 representative crystals from this group. It was shown that the lattice constant is a linear function of the ionic radii and electronegativity of the constituting ions. A simple empirical equation was obtained as a result of the performed analysis. It gives very good agreement between the experimental and modeled values of the lattice parameters, with an average error of 1.05%. The developed approach can be efficiently used for a simple, fast, and reliable prediction of lattice constants and interionic distances in isostructural materials having a similar composition.     

The formation of oxide nanoparticles on the surface of natural clinoptilolite

Nanoparticles of NiO, ZnO and Cu₂O crystallize when the Ni-, Zn- and Cu-exchanged natural clinoptilolite, respectively, are dehydrated by heating in air at 550 °C. The dehydration of Mn-exchanged clinoptilolite does not lead to the crystallization of manganese oxide but affects the crystallinity of the host clinoptilolite lattice, which becomes amorphous. The NiO, ZnO and Cu₂O nanoparticles are found to be randomly dispersed in the clinoptilolite matrix. The particle size varies from 2 to 5 nm and exceeds the aperture of the clinoptilolite channel (approximately 0.4 nm), suggesting that the crystallization of the oxide phases takes place on the surfaces of clinoptilolite microcrystals.     

The ESR study of single crystal spinel ZnCr2Se4 diluted with Sb and V

The single crystal of Sb³⁺ and V³⁺ doped zinc chromium selenide spinel ZnCr₂Se₄ were prepared by a chemical transport method and characterized by ESR spectroscopy in order to examine the effect of nonmagnetic antimony and magnetic vanadium on properties of the system. For antimony admixtures the Neel temperature is very similar to that of the parent spinel ZnCr₂Se₄ (22 K). However, upon incorporating vanadium ions, the T_N temperature decreases down to 17.5 K, determined for the maximum vanadium content (x=0.06). The temperature dependence of the ESR linewidth over paramagnetic region is interpreted by an occurrence of spin-phonon interaction. The strong broadening linewidth together with its strong temperature dependence for vanadium doped ZnCr₂Se₄ is explained by the complex paramagnetic relaxation model.     

Geometrically distributed aperiodic circular photonic crystals with broad and isotropic photonic band gaps

In this paper, a new type of circular photonic crystal (CPC) with a geometrical distribution of concentric layers is presented. A broad and isotropic photonic band gap is achieved using this geometrically distributed CPC (GCPC). Also, the influence of the number of concentric layers to the overall band gap of GCPC is studied. It is demonstrated that the band gap broadens with a red shift when the number of concentric layers is increased. The reason for the red shift of the band gap is further investigated.     

基于异面交会的空中运动目标定位算法及误差分析

介绍了空中运动目标定位测量的经纬定位仪单站定向和双站异面交会定位原理,并对影响定向和定位结果的各个因素进行了误差分析和仿真.结果表明,交会角在[40°,165°]时.测量精度有明显地改善,为组网测量布站提供了依据.黑火药爆炸试验测量结果验证了该方法的可行性和测量精度.     

CBERS-02B星HR相机内方位元的在轨标定方法

遥感相机内方位元素的在轨标定对遥感图像的定位和测量具有重要意义.利用线阵推扫传感器构像模型,提出了一种对CBERS-02B星HR相机内方位元素进行在轨标定的方法.该方法以内方位元素和姿态角为未知参数,建立地面控制点和相应像点的共线方程组,通过解算共线方程组获得内方位元素.实验证明,用该方法对内方位元素进行在轨标定,具有...     

Thermal and dielectric studies of nickel malonate dihydrate single crystals

Single crystals of nickel malonate dihydrate were grown by the gel technique, employing the single diffusion method. Thermal dehydration of the crystal was investigated by thermogravimetric and differential thermal analyses. The title compound exhibits a steady thermal behaviour at higher temperature range of 350-800 °C. The dielectric properties of the prepared sample were analyzed as a function of frequency in the range of 1 kHz-1 MHz and at temperatures between 40 and 140 °C.     

Structural, elastic and electronic properties of a new ternary-layered Ti2SiN

The structural, elastic and electronic properties of Ti₂SiN were studied by first-principle calculations. The calculated bond lengths of Ti-Si and Ti-C are 2.65 and 2.09 Å, respectively. The results show Ti₂SiN is mechanically stable, and its bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio μ and anisotropy factor A are determined to be 182 GPa, 118 GPa, 291 GPa, 0.233 and 1.57, respectively. The calculated electronic structure indicates that Ti₂SiN is anisotropic and conductive.