Off-center substitutional ions in alkali-halide crystals

The potential wells of alkali and halogen ions as impurities in alkali halides are investigated by means of a deformation-dipole model with single-ion parameters. The calculations indicate that Li⁺ is off center in seven and F^? in six of the sixteen rocksalt-type crystals considered. In about half of the off-center systems the configuration has D_4h symmetry if the impurity is kept at its lattice position. The minimum-energy configuration of the off-center system KCl:Li⁺ is calculated in detail, and the influence of hydrostatic pressure is investigated. Our results are in qualitative agreement with experiment.     

Mass dependence of the ground state of charged particles in a silicon crystal

We report a quantum-mechanical study of the ground state of a positively charged particle in an otherwise perfect Si crystal. Particles with intermediate masses between the positron and the deuteron are considered. We find that there are two substantially different limit behaviours, depending on the mass value, ranging from the extreme localization in the high-electronic-density region of the deuteron wave function to the almost uniform extension of the positron one, which on the contrary attributes the maximum of probability to the interstitial region. Moreover, we underline the behaviour of the intermediate mass particles, μ⁺ and π⁺, which exhibit a significant degree of delocalization of their wave functions.     

碱熔融-电感耦合等离子体原子发射光谱法测定氧化铟锡烧结混合粉中5种杂质元素

采用氢氧化钠熔融样品,热水浸取后盐酸酸化,建立了碱熔融-电感耦合等离子体原子发射光谱(ICP-AES)法测定氧化铟锡烧结混合粉中Fe、Ca、Mg、Al和Si等元素的分析方法.试验结果表明:称取0.500 0 g试样,加入0.80 g氢氧化钠,在灰化炉中熔融120 min,可将样品完全溶解.基体铟和锡的干扰采用基体匹配法消除,被测元素之间没有光谱干扰.钠盐对硅的测定有一定影响,可在标准溶液中加入一定量氢氧化钠予以消除.对方法进行精密度和加标回收试验,测得结果的相对标准偏差均小于5%,方法加标回收率在90%~105%之间.     

ICP-AES法测定高纯氧化铕中稀土杂质元素

研究了锌粉还原 5709萃淋树脂分离富集 ICP AES法测定高纯氧化铕中14个稀土杂质元素的方法,用ICP AES法测定稀土元素工作曲线下限为(以氧化物计)镧为0.05mg·L-1,铈、镨、钇为0.25mg·L-1,钕、钐、铽、镝、钬为0.1mg·L-1,铒、铥、镱、镥、钇为0.05mg·L-1,回收率为90%～106%。方法简便、准确、快速,可用于99.99%氧化铕中14个稀土杂质元素的测定。     

Ab Initio Modeling of Interatomic Interactions in 3C–SiC:M, M = Cr, Mn, Fe, Co

The electronic structure and chemical binding parameters of impurity atoms M = Cr, Mn, Fe, Co in cubic silicon carbide are considered in DFT (density functional theory) and X-DV (discrete variation) approximations. A scheme for calculating the binding energies in the cluster approach is suggested. Stoichiometric and superstoichiometric models of impurity incorporation are investigated. The binding energy is higher for the stoichiometric model. In the superstoichiometric model, the titanium and iron atoms preferably occupy the Si₄ interstice. For all other atoms, the MSi, Sii model is preferable. The incorporated impurity weakens the basic Si–C bonds.     

High intensity magnetic fields for the identification and study of donors in epitaxial gallium arsenide

High intensity magnetic fields are needed for the far infrared photoconductivity method to be used reliably in the identification of unitentional contaminants in ultra high purity epitaxial GaAs. We show experimental evidence that the inhomogeneous Stark broadening of the 1s2p (m=–1) transition of the hydrogen-like donor almost disappears as the magnetic field is increased to 20 Tesla. Since the spectral lines also become narrower and the central cell correction (chemical shift) becomes larger, the signature curve method of identification permits positive identification of donor species. In particular, the donors Ge and Se have been identified in specimens that were reported to contain carbon and Sn respectively.Work supported by the U.S. Air Force Office of Scientific Research under Grant #AFOR-78-3708.Supported by the National Science Foundation.     

离子色谱法在氢燃料电池汽车用氢气中的应用现状及展望

氢燃料电池汽车用氢气中痕量杂质会影响氢燃料电池的性能,国内外标准均严格规定了痕量杂质的限值要求。离子色谱法（IC） 具有操作简单、分析快速、灵敏度高、选择性好、可多组分检测的特点,ISO 14687－2∶2012、SAE J2719∶2015和GB/T 37244－2018等标准均涉及到离子色谱法分析其中的部分指标。目前离子色谱法在环境空气、固定污染源废气、天然气、烟气等气体分析领域有广泛应用,在氢燃料杂质的分析领域尚在起步阶段。该文综述了氢燃料和其他气体分析领域中总卤化物、甲酸、氨和总硫化物的分析方法,将离子色谱与不同分析技术进行比较。并基于离子色谱在其他气体杂质分析领域的应用进展,对其在氢燃料电池汽车用氢气杂质分析中的应用作出展望。     

Gd-substituted Bi-2223 superconductor

The effects of gadolinium doping at calcium site on the normal and superconducting properties of Bi-2223 system were studied. The Gd-doped (BiPb)-2223 series of specimens, namely Batch I, II and III were sintered at three different sintering temperatures 830, 850 and 895°C respectively. The properties investigated are (1) the normal state resistivity with a view to study metal-to-insulator transition, (2) the XRD patterns of the specimens with a view to study the relative composition of (BiPb)-2212 and (BiPb)-2223 phases and (3) the superconducting fluctuation behaviour (SFB) with a view to determine the effect of doping, if any, on the dimensionality of the fluctuation conductivity of the system. The normal state resistivity of Gd-substituted Bi-2223 specimens shows metallic, semiconducting and insulating behaviour. The T _c (R = 0) values indicate that (BiPb)-2223 phase is responsible for the observed superconducting transitions in Batch I and Batch II specimens with Gd concentrations x ≤ 0.7. This observation is further confirmed in the analysis of XRD patterns of these specimens. Gadolinium, being a magnetic impurity, has pair breaking effect near the Fermi level and decreases T _c (R = 0). The analysis of the superconducting fluctuation behaviour (SFB) shows a 2D dimensionality without any cross-over.

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Quantitative Determination of Four Potential Genotoxic Impurities in the Active Pharmaceutical Ingredients in TSD-1 Using UPLC-MS/MS

A novel method of ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was developed for the identification and quantification of four potential genotoxic impurities (PGIs) in the active pharmaceutical ingredients of TSD-1, a novel P2Y₁₂ receptor antagonist. Four PGIs were named, 4-nitrobenzenesulfonic acid, methyl 4-nitrobenzenesulfonate, ethyl 4-nitrobenzenesulfonate, and isopropyl 4-nitrobenzenesulfonate. Following the International Conference of Harmonization (ICH) guidelines, this methodology is capable of quantifying four PGIs at 15.0 ppm in samples of 0.5 mg/mL concentration. This validated approach presented very low limits (0.1512–0.3897 ng/mL), excellent linearity (coefficients > 0.9900), and a satisfactory recovery range (94.9–115.5%). The method was sufficient in terms of sensitivity, linearity, precision, accuracy, selectivity, and robustness and, thus, has high practicality in the pharmaceutical quality control of TSD-1.     

Surface and grain boundary segregation in 16MND5 steel

An adequate model of quantification when there are many segregating elements is required for industry and research. Hence, for the first time, surface segregation kinetics on industrial 16MND5 steel was studied by XPS spectroscopy at temperatures ranging from 500 to 600 ^oC. From measurements that highlight the competitive segregation of P, S, Sn, Sb, As, and Cu impurities at the surface, a quantification model was developed and successfully used to deduce the surface concentrations during segregation kinetics as well as derive the corresponding diffusion coefficients. We observed that phosphorus and sulfur are the first elements covering the surface, then they are supplanted by others' impurities. This result may reflect impurities segregation behavior at the grain boundaries that impacts mechanical behavior of the material. Indeed, to further the research, 16MND5 samples were aged in the same range of temperatures. Then, Auger spectroscopy measurements at grain boundaries were conducted on broken samples exhibiting intergranular cracking. Results show that phosphorus is the only segregating element present at grain boundaries after 2 months of aging. Importantly, it appears that phosphorus grain boundary segregation kinetics is significantly lower than at surface. Copyright © 2017 John Wiley & Sons, Ltd.