Molecular dynamics simulations of the formation for NaCl cluster at the interface between the supersaturated solution and the substrate

Molecular dynamics simulations of supersaturated aqueous NaCl solution including the Pt(100) or NaCl(100) crystal surfaces have been performed at an average temperature of 298 K. The behavior of the NaCl cluster produced in the solution have been studied through the consideration of the water dielectric property near the crystalline surfaces for understanding the role of crystal growth on the surface. The surfaces in the solutions greatly influence heterogeneous nucleation in crystallization process. Density profile of the supersaturated solution and polarization of water molecules was calculated in order to describe the effect of the surfaces on the solution structure at the solid–liquid interfaces. The formation levels of NaCl clusters heavily depended on the water orientation at the interfaces. NaCl clusters were easily formed near the Pt(100) surface compared with the NaCl(100) surface owing to a different construction of water molecules between the platinum and NaCl surface.     

Strong dc electric field applied to supersaturated aqueous glycine solution induces nucleation of the gamma polymorph

Applying a strong static electric field to supersaturated aqueous glycine solutions resulted in the nucleation of the gamma polymorph. This is the first report of a strong dc field inducing the nucleation of a neutral solute in a supersaturated solution. We attribute this effect to the electric-field-induced orientation of the highly polar glycine molecules in large preexisting solute clusters, helping them organize into a crystalline structure. This result also lends further support to our proposed optical-Kerr mechanism for nonphotochemical laser-induced nucleation.     

Dehydration process in NaCl solutions under various external electric fields

Ionic motions at solid-liquid interface in supersaturated NaCl solutions have been investigated by molecular dynamics (MD) simulation for understanding crystal growth processes. The density profile in the vicinity of the interfaces between NaCl(100) and the supersaturated NaCl solution was calculated. Diffusion coefficients of water molecules in the solution were estimated as a function of distance from the crystal interface. It turned out that the structure and dynamics of the solution in the interfaces was different from those of bulk solution owing to electric fields depending on the surface charge. Therefore, the electric field was applied to the supersaturated solutions and dehydration phenomenon occurring in the process of the crystal growth was discussed. As the electric field increased, it was observed that the Na⁺ keeping strongly hydration structure broke out by the electric force. In supersaturated concentration, the solution structure is significantly different from that of dilution and has a complicated structure with hydration ions and clusters of NaCl. If the electric fields were applied to the solutions, the breakout of hydration structure was not affected with increasing the supersaturated ratio. This reason is that the cluster structures are destroyed by the electric force. The situation depends on the electric field or crystal surface structure.     

应用分子动力学模拟和拉曼光谱对钙、镁、氯离子 水化现象的研究

应用分子动力学方法,模拟了298 K下,密度为1.0 g/cm~3的水溶液中Ca²⁺,Mg²⁺,Cl~-的水化现象,得到了相应离子周围水分子的微观分布情况.发现在钙离子周围,水分子以其氧离子去靠近中心离子;而在氯离子周围,水分子则以其中的一个氢原子去靠近中心离子.通过分析三种离子的径向分布函数、配位数曲线、水化数、水化半径,发现Ca²⁺的水化数和水化半径均大于Mg²⁺,即Ca²⁺的水合能力比Mg²⁺强.与以往研究结果相比,本文计算所得的自扩散系数更接近实验所得结果.为了使模型更好的代表真实水溶液体系,本文还应用分子动力学和拉曼光谱法研究了不同浓度的CaCl₂水溶液.分子动力学研究发现随着浓度的升高,CaCl₂溶液中Ca²⁺,Cl~-的配位数分别呈降低趋势.同时,随着浓度的升高,Ca²⁺,Cl~-的自扩散系数也呈现降低的趋势.作者推断这是由于浓度的升高,加剧了离子的微观反...     

丙二醇甲醚中超痕量金属杂质元素的ICP-MS/MS分析

基于电感耦合等离子体串联质谱（ICP-MS/MS）建立了准确测定丙二醇甲醚中超痕量金属杂质元素的分析方法,提出了利用混合反应气消除质谱干扰的新策略。丙二醇甲醚经超纯水稀释后直接采用ICP-MS/MS测定其中具有挑战性的超痕量金属元素Mg,Al,K,Ti,V,Cr,Fe,Ni,Cu和Zn,在MS/MS模式下,选择混合气NH₃/He/H₂为反应气,Ti+,Cr+,Fe+,Ni+,Cu+,Zn+与NH₃发生质量转移反应,在形成的团簇离子中,Ti(NH₃)+₆,Cr(NH₃)+₂,Fe(NH₃)+₂,Ni(NH₃)+₃,Cu(NH₃)+₂和Zn(NH₃)+丰度高且无干扰,利用NH₃质量转移法将Ti+,Cr+,Fe+,Ni+,Cu+和Zn+转移为相应的团簇离子进行测定;H₂能与加合物-NH和-NH₂反应生成-NH₃,增大碰撞/反应池（CRC）内-NH₃的浓度,有利于提高Ti,Cr,Fe,Ni,Cu和Zn的分析灵敏度。Mg+,Al+,K+和V+几乎不能与NH₃反应,而干扰离子能与NH₃反应形成团簇离子,可以利用NH₃原位质量法进行Mg,Al,K,V的测定;H₂能快速与Ar基干扰离子发生反应,而与其他离子的反应速度很慢,反应气中加入H₂能迅速彻底消除Ar基干扰离子所形成的质谱干扰,有利于Mg,Al,K和V的测定。优选Sc+与NH₃反应生成的团簇离子Sc(NH₃)+₅为Ti(NH₃)+₆,Cr(NH₃)+₂,Fe(NH₃)+₂,Ni(NH₃)+₃,Cu(NH₃)+₂和Zn(NH₃)+的内标离子,Be+与NH₃反应生成的团簇离子Be(NH₃)+₄为Mg+,Al+,K+和V+内标离子,校正了样品溶液,标准溶液和空白溶液之间由于物理化学性质差异产生的基体效应,确保了分析信号的稳定。将所建立的方法应用实际样品的加标回收实验,并采用双聚焦扇形磁场电感耦合等离子体质谱（SF-ICP-MS）进行对比分析,评价分析方法的准确性。结果表明,各元素的检出限为0.52～61.5 ng·L-1,加标回收率为95.6%～104.2%,相对标准偏差（RSD）≤4.5%;在95%的置信度水平,所有元素的分析结果与SF-ICP-MS的测定结果无显著性差异,验证了分析方法的准确性好,精密度高。将方法应用于丙二醇甲醚中超痕量金属杂质元素的测定,具有分析速度快,无干扰,灵敏度高的优势。     

采用分子动力学方法研究氯化钠水溶液的微观结构

溶液的微观结构对溶液的宏观性质具有决定性影响,团簇的存在和溶液不均性的认知是该领域研究的重要进展之一,也是关注的热点.为了考察溶液的微观结构,本文采用分子动力学方法对浓度适中的氯化钠水溶液进行了模拟,获得了各原子(离子)间的径向分布函数和溶液的瞬态图像.通过对比分析Na~+-Cl~-和Cl~--Na~+的径向分布函数,并结合已有研究结果,表明该径向分布函数上第三峰也来源于离子对,发现氯化钠水溶液存在着第三种离子对;上述径向分布函数上的三个峰分别与直接接触离子对、部分间隔离子对和完全间隔离子对相对应,并给出了这三种离子对的瞬态图像.三个时刻下系统瞬态图像的分析结果表明,溶液中存在水分子连续分布的区域和由离子与水分子共同构成的离子团簇.各瞬态图像中水分子连续分布的最大区域的平均尺寸至少为1.43 nm,溶液中部分间隔离子对的比例最大,约为0.68.在同时考虑直接接触离子对和部分间隔离子对时,三个时刻中最大团簇尺度的平均值为1.44 nm,该值约为部分间隔离子对最概然尺寸的3倍;团簇尺寸随团簇中离子数的增加而增大,在团簇中离子数较大时,满足无规行走(自由连接链)模型的结果.这些说明氯化钠水溶...     

团簇分子[Zn-(CH_3CH_2OH)_n]~(2+)的荧光光谱研究及理论光谱验证

通过荧光光谱实验和理论计算对金属离子在乙醇溶液中的微团簇结构进行了研究。荧光光谱实验发现在275~330 nm范围存在较强的乙醇分子荧光峰,当加入盐离子(Zn~(2+))后该处荧光强度逐渐变弱,说明盐的加入对乙醇体系的荧光效率产生了影响,破坏了原有乙醇分子之间的作用,使得其刚性结构发生改变,荧光效率降低,同时Zn~(2+)与乙醇分子通过溶剂化作用形成了新的微团簇,在350~380 nm之间出现了新峰。通过对团簇结构[Zn-(H_2O)_n]~(2+)(n=1~3)进行优化比较,得到了相对精确及运算成本较低的密度泛函理论B3LYP方法,并应用于Zn~(2+)在乙醇溶液中团簇结构计算。结果表明体系的第一溶剂化层存在着n=1~6的微团簇分子,且最多为6。比较理论计算荧光光谱与实验荧光光谱,进一步说明了Zn~(2+)与乙醇形成了新的微团簇及计算方法的可行性。     

氯化钾水溶液微观结构的分子动力学模拟研究

氯化钾水溶液不同于氯化钠的,其在低温下只能形成无水盐和冰.现有研究表明在氯化钠水溶液中不仅存在着水分子连续分布的区域与离子团簇,而且这二者的物质组成也与该溶液所形成晶体的分别对应.为了探寻其他溶液中是否存在此类对应关系,并考察溶液的微观结构,本文采用分子动力学方法对氯化钾水溶液进行了研究,表明了该溶液的一些性质.氯化钾水溶液中K⁺-K⁺和Cl^--Cl^-径向分布函数的特征具有一致性,峰的最大值所对应的位置都分别相同,明显不同于氯化钠水溶液的.系列时刻下瞬态图像内O到其最近离子距离中最大值的统计结果表明氯化钾水溶液中存在着一定大小的水分子连续分布的区域,其平均尺寸至少为2.26 nm;瞬态图像中K⁺与其最近邻Cl^-之间的距离主要分布在0.28 nm～0.38 nm之间,占比约为97.4%;溶液中存在着较大和较小两类离子团簇,较大团簇的平均尺寸为1.73nm,平均离子数是25.0,其内部的离子与周围离子之间具有与氯化钾晶体类似的结构;这些结果表明氯化钾水溶液中也...     

Magnetic resonance of spin clusters and triplet excitations in a spin-Peierls magnet with impurities

The magnetic resonance spectrum of spin clusters formed in spin-Peierls magnets in the vicinity of impurity ions is investigated. The observed temperature dependences of the effective g-factor and the linewidth of the electron paramagnetic resonance (EPR) in crystals of Cu_1?x Ni_xGeO₃ are described in the model of the exchange narrowing of the two-component spectrum with one component ascribed to spin clusters and exhibiting an anomalous value of the g-factor and the other related to triplet excitations. An estimation of the size of the suppressed dimerization region around the impurity ion is obtained (this region includes about 30 copper ions). The dependence of the effective g-factor and the EPR linewidth on the impurity concentration at low temperatures indicates the interaction of clusters.     

黑龙江穆棱地区宝石级石榴石的宝石学及谱学特征

对黑龙江穆棱新生代玄武岩产出的宝石级石榴石进行了宝石学常规测试、电子探针测试、拉曼光谱、红外光谱和紫外-可见光谱测试,以获得该区石榴石的宝石学特征和谱学特征。化学成分分析表明,该区石榴石为镁铝榴石,含有Fe,Ca,Mn,Cr,Ti等杂质元素。其平均晶体结构化学式为 (Mn_0.022Ca_0.455, Fe2+_0.720, Mg_1.793)_∑=2.990(Ti_0.003Cr_0.009Fe3+_0.062Al_1.951)_∑=2.025(SiO₄)₃。拉曼光谱分析表明该区石榴石存在混合相,由石榴石桥氧振动引起的拉曼位移峰反映出该特征。镁铝榴石桥氧弯曲振动拉曼位移峰位于560 cm-1(A₁g模)和641 cm-1(E_g+F₂g模),钙铝榴石和铁铝榴石桥氧弯曲振动E_g+F₂g模形成的拉曼位移峰分别位于507和486 cm-1。官能团区红外光谱显示该区镁铝榴石中不存在分子水,但少数镁铝榴石中存在少量的结构水,它们在3 585,3 566和3 544 cm-1处形成阶梯状的弱小吸收峰。该区镁铝榴石多为褐红色,其颜色由杂质离子Cr3+,Fe3+,Mn2+产生。紫外-可见吸收光谱显示,Fe3+的电子跃迁致570,521和502 nm吸收峰,Mn2+的电子跃迁致460和430 nm吸收峰,Cr3+电子跃迁致690和367 nm吸收峰。     

Atomic and molecular defects in solid He

The studies of defects formed by impurity particles (atoms, molecules, exciplexes, clusters, free electrons, and positive ions) embedded in liquid and solid ⁴He are reviewed. The properties of free electrons and neutral particles in condensed helium are described by the electron (atomic) bubble model, whereas for the positive ions a snowball structure is considered. We compare the properties of the defects in condensed helium with those of metal atoms isolated in heavier rare gas matrices.     

Application of High-Frequency Electron Paramagnetic Resonance/Electron Spin Echo for the Identification of the Impurity Composition and Electronic Structure of Ceramics Based Garnets

Physics of the Solid State - Electron paramagnetic resonance (EPR) spectra of Ce3+, Yb3+, Cr3+, and Gd3+ impurity ions in yttrium aluminum garnet Y3Al5O12 (YAG) ceramics were detected and...     

Molecular self-organization of Ho<Superscript>3+</Superscript> impurity ions in synthetic forsterite

The structure of paramagnetic centers formed by impurity Ho³⁺ ions in synthetic forsterite is studied by submillimeter EPR spectroscopy in the frequency range 65–200 GHz. It is found that Ho³⁺ enters into the Mg²⁺ sublattice in the form of single ions and dimer centers. The concentration of dimer centers considerably exceeds the concentration of single ions, which points to the molecular self-organization of Ho³⁺ impurity ions into dimers during the growing of the crystals from melt. Possible structures of the dimer center are discussed. The parameters of the effective spin Hamiltonian describing the behavior of the electron-nuclear sublevels of the two lowest electronic levels of the Ho³⁺⁵I₈ ground multiplet are determined for a single ion and a dimer center.     

Ti：Al2O3晶体的电子自旋共振谱研究

Ｔｉ：Ａｌ２Ｏ３晶体中的顺磁中心Ｔｉ＾３＋由于强烈的晶格自旋耦合而使其电子自旋共振吸收只有在液拟温度附近才能看到，本实验在液氮温度附近记录到由许多强的的吸收峰迭加于Ｔｉ＾３＋宽吸收线所组成的电子自旋共振谱，这些吸吸收峰被认为是Ａｌ２Ｏ３基质中的Ｆｅ＾３＋，Ｍｎ＾２＋，Ｃｒ＾３＋，Ｍｏ＾３＋，Ｆｅ＾２＋，Ｃｏ＾２＋等杂质的共振吸收及Ｔｉ＾２＋３Ａ２ｇ基态的双量子跃迁造成的。     

Charged clusters in liquid helium

The appropriateness of the experimental study of charged clusters in liquid helium has been supported. The interaction potential of negative ions (electron bubbles) with inert clusters formed by Ne, Ar, Kr, and Xe atoms or H₂ and N₂ molecules has been found. Small clusters levitate at a distance of 13–16 Å above the negative ion. The scalings laws for the properties of charged inert clusters have been discovered and grounded; the number of quantum levels and states of such clusters has been determined. The mobility measurement of charged clusters may provide a new technique of probing the properties of impurity nanoparticles in helium.     

Spectroscopy of radiation-induced and structural defects in garnet crystals with V and Cr impurity ions

The optical absorption spectra of crystals with garnet structure (A₃B₂C₃O₁₂), containing V or Cr impurity ions, before and after oxidation annealing, γ irradiation, and coactivation with Ca and Mg ions have been experimentally and theoretically investigated. It is shown that V³⁺ and Cr⁴⁺ ions are incorporated into both octahedral and tetrahedral sites of the garnet lattice. The absorption spectra and energy level diagrams of impurity ions are identified.     

Fluorescence Properties of Frog Skeletal Muscles Treated with Lanthanide Ions

Laser-induced fluorescence from frog skeletal muscle fibers treated with lanthanides, Eu³⁺ and Tb³⁺, was recorded. The fluorescence was weak and overlapped with the Raman scattering by the Ringer solution when the muscle fibers were illuminated with an argon-ion laser. The fluorescence decay rate of the lanthanide in Ringer's solution was 2–3 times larger than that of the lanthanide bound to the muscle fiber. The number of water molecules coordinated to the lanthanide bound to the muscle fiber was determined to be about three. This suggests that lanthanide ions bind superficially to the outer membrane of the muscle fiber.     

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

We have studied the magneto-optic Faraday effect (FE) and electron paramagnetic resonance (EPR) in an aluminum potassium borate glass containing Fe oxides as an impurity in a concentration of 1.5 mass % and Mn impurity in variable concentration from 0 to 1.2 mass %. When manganese oxide is added to the glass composition, the paramagnetic contribution to the Faraday effect increases more slowly than the change in the total concentration of paramagnetic ions, which allows us to hypothesize the appearance of clusters in which the paramagnetic ions are coupled by antiferromagnetic interactions. Formation of clusters upon addition of manganese oxide is confirmed by the change in the nature of the EPR spectra, where we observe a manganese concentration dependence of the distribution of iron atoms with respect to the different positions in the glass matrix. Heat treatment leads to a strong increase in the Faraday effect and a change in the spectral dependences of the Faraday effect and the EPR, which is explained by enlargement of the clusters and appearance of nanoparticles. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 354–358, May–June, 2006.     

ICP与吸收光谱测定LiNbO3, Zn:LiNbO3晶体中Cr3+离子的分布及有效分凝系数

应用坩埚下降法生长了掺杂Cr与双掺杂Cr，Zn的LiNbO3晶体。测定了掺杂晶体不同部位的吸收系数。用电感耦合等离子体原子发射光谱(ICP)法测定了Cr离子在LN晶体中的浓度，并计算了Cr离子在LiNbO3晶体中的有效分凝系数。研究结果表明：在单掺杂Cr的LiNbO3晶体中，随着Cr^3 掺杂浓度从0．1增加到0．5mol％时，其有效分凝系数从3．75减少到2．49，Cr^3 离子在晶体中的浓度分布差异逐步减少；ZnO的掺入能有效地减少Cr^3 的分凝系数，然而ZnO掺杂浓度从3增加到6mol％时，其有效分凝系数且从1．85增加到2．25。可从ZnO组分对Cr离子的排斥作用及Zn离子在LN晶体中随掺杂数量变化的分凝现象解释了产生Cr离子浓度及有效分凝系数变化的原因。     

Dislocation nucleation and precipitation of impurity in calcium-doped NaCl-KCl crystals

In calcium-doped mixed NaCl-KCl crystals, Ca²⁺ ion sites were selectively sensed by a suitable etchant. Different impurity substructures, viz. arrays, close-networks, unevenly distributed clusters were formed by the dopant ions in the lattice. Non-uniform distributions of the impurity ions in the lattice does not nucleate dislocations. Non-structural impurities like precipitates were found to take different forms, viz. elongated rods, rectangular forms, with different orientations. Dislocations showed strong preference for the nucleation of the precipitates. The nucleation of the precipitates at sites other than those of dislocations is discussed.