Long-range coulomb interaction in ionic crystals

Expressions have been proposed for calculating the matrix elements of the Coulomb interaction of p and d electrons in a chosen ion of a crystal with an infinite crystal lattice. The matrix elements have been calculated at Gaussian-type orbitals. The Coulomb interaction energy per molecular unit of the ????-NaV₂O₅ crystal has been calculated in the ionic approximation for homogeneous and chain orderings. It has been shown that the more correct determination of the energetic favorability of one or other ordering requires calculation of the Coulomb interaction energy with an infinite crystal lattice of electrons that are at different orbitals of the ion under consideration.     

Doping strategies for increased performance in BiFeO3

Investigation of crystal structure, dielectric, magnetic and local ferroelectric properties of the diamagnetically substituted Bi_1−xA_xFeO_3−x/2 (A=Ca, Sr, Pb, Ba; x=0.2, 0.3) polycrystalline samples has been carried out. It has been shown that the heterovalent A²⁺ substitution result in the formation of oxygen vacancies in the host lattice. The solid solutions have been found to possess a rhombohedrally distorted perovskite structure described by the space group R3c. Piezoresponse force microscopy has revealed signs of existence of the ferroelectric polarization in the samples at room temperature. Magnetization measurements have shown that the magnetic state of these compounds is determined by the ionic radius of the substituting elements. A-site substitution with the biggest ionic radius ions has been found to suppress the spiral spin structure of BiFeO₃ giving rise to the appearance of room-temperature weak ferromagnetism.     

广寄生及其不同寄主黄酮总量和微量元素含量的研究

用紫外分光光度法测定广西玉林产5种广寄生及其不同寄主的黄酮总量;原子吸收分光光度法测定广寄生和寄主的Fe、Mg、Zn、Ca、Mn、Cu、Na、K8种微量元素的含量。结果表明:寄主不同,广寄生黄酮总量和微量元素含量存在差异;广寄生的黄酮总量比寄主高,广寄生的K、Mg元素含量比寄主高。     

General relationships for isovalent cation substitution into oxides with the rocksalt structure

Isovalent cation substitution into rocksalt oxides, MO, has been investigated using atomistic simulation. A strain related parameter, ε, is established that relates the size of a substitutional cation to the host lattice ion for which it has been substituted. This has allowed us to identify relationships between solution energy, defect volume and a strain parameter, which are general for any rocksalt oxide host lattice and as such are predictive for any combination of a divalent cation and rocksalt host lattice.     

Trace anomaly and dimension two gluon condensate above the phase transition

The dimension two gluon condensate has been used previously within a simple phenomenological model to describe power corrections from available lattice data for the renormalized Polyakov loop and the heavy quark-antiquark free energy in the deconfined phase of QCD [1,2]. The QCD trace anomaly of gluodynamics also shows unequivocal inverse temperature power corrections which may be encoded as dimension two gluon condensate. We analyze lattice data of the trace anomaly and compare with other determinations of the condensate from previous references, yielding roughly similar numerical values.     

Symmetry breaking and restoring under high pressure: the amazing behaviour of the “simple” alkali metals

We argue that an ionic lattice surrounded by a Fermi liquid changes phase several times under pressure, oscillating between the symmetric phase and a low-symmetry dimerized structure, as a consequence of Friedel oscillations in the pair potential. Phase oscillations explain the tendency towards dimerization which has been recently reported for the light alkali metals under high pressure. Moreover, a restoring of the symmetric phase is predicted for such elements at an even higher density. Received 17 January 2003 Published online 11 April 2003 RID="a" ID="a"e-mail: giuseppe.angilella@ct.infn.it     

The volume dependent total energy of metals and the ionic radii

The cohesive energies, lattice constants and compressibilities for a number of metals are correlated with the ionic radii through second order pseudo-potential theory. The model yields reasonable results not only for simple metals of arbitrary valency, but for transition elements with no more than 5 d-electrons.     

Structure of electromagnetic fields near the surface of an ionic crystal

A NaCl ionic crystal whose (100) face is in contact with vacuum is used as an example to consider static and dynamic contributions to an electromagnetic field in close proximity to its surface. The expression for the potential of the electric field produced by a system of point charges in vacuum (derived by Lennard-Jones and Dent) is taken as the basis. The dynamic correction to the static field has been found. It appears as a result of thermal fluctuations of ions near equilibrium positions in the ionic lattice. Various contributions of the electrostatic field of the ionic lattice, the field of fluctuating ions of this lattice near their equilibrium positions, and of the dipole-type fluctuation field produced by spontaneous deformations of the crystal??s elementary cells to the energy density of the electromagnetic field near the surface of the ionic crystal have been calculated and compared. The periodic structuring of the electromagnetic field??s energy density caused by the presence of static and dynamic ionic lattices of the crystal at small distances from its surface is illustrated graphically. Fields generated by a film with a finite thickness containing an arbitrary number of ion monolayers have also been considered.     

ICP-AES法测定茶叶、茶水中的矿物质和微量元素

本文用电感耦合等离子体原子发射光谱法（ICP－AES）对不同品种，不同等级及不同产地的茶叶、茶水样品中的一些人体所必需的矿物质和微量元素进行了定量测定。结果表明，该方法简便，可靠，具有良好的精密度和准确度，本研究将对茶叶中一些矿物质和微量元素的鉴定以及在饮茶爱好者的合理购茶、饮茶等方面提供一些有用的信息。     

Comment on “Prediction of lattice constant in cubic perovskites”

In a recent work by Jiang et al. [Prediction of lattice constant in cubic perovskites, J. Phys. Chem. Solids 67 (2006) 1531-1536], the interrelationship between lattice constant, ionic radii and tolerance factor of cubic perovskites has been established and an empirical equation was obtained. However, the assumption of incorrect ionic coordination led to an incorrect mathematical expression even though the average relative errors between predicted and observed lattice constants of 132 materials were below 1%. Here, corrected coefficients for that empirical expression are obtained, which would likely be useful for investigation of general perovskite materials.     

Site selectivity of dopant cations in Ca3(SiO4)Cl2

A series of static lattice calculations were performed to determine the site selectivity of cations of differing size and valence when substituted onto the Ca sites of the calcium chlorosilicate (Ca₃(SiO₄)Cl₂) lattice, a potential host phase for the immobilisation of halide-rich wastes arising from the pyrochemical reprocessing of plutonium. Atomic-scale simulations indicate that divalent cations are preferentially substituted onto the Ca1 site, whilst tri- and tetravalent cations are preferentially hosted on the Ca2 site, with the Ca1 site favoured for forming the vacancies necessary to charge-balance the lattice as a whole. Multi-defect calculations reveal that the site selectivity of the dopant cations is dependent on their ionic radii; as the ionic radii of the divalent cations increase, substitution onto the preferred site becomes more and more strongly favoured, whereas the inverse is true of the trivalent cations.     

氢化物发生-原子荧光光谱法测定地质试样中的痕量锗

试验了原子化器温度，灯电流，负高压，载气流量等对原子荧光测定锗的灵敏度及线性范围的影响，考察了共存元素的干扰情况，选定了最佳工作条件，对国家土壤一级标准物质中痕量锗进行测定，测定值与标准值吻合。     

中草药中多种微量元素的ICP-AES同时测定研究

本文提出了中草药漏芦中多种微量元素的等离子体原子发射光谱（ＩＣＰ－ＡＥＳ）同时测定的方法,并以ＧＢＷ０８５０１桃叶标准样进行对照测定。标准样的测定值与参考值吻合较好,试样分析结果满意。该方法具有灵敏、准确及多元素同时测定,操作简便,快速等优点,适应于中草药及其各种剂型中多元素同时测定。     

淡水和海水养殖珍珠的微量元素特征

珍珠中的微量元素有其特征规律及作用。前人很早就关注到淡水珍珠和海水珍珠微量元素特征的差异,但限于测试技术及分析方法,测出的微量元素种类相当有限,并且对测试结果也缺乏深入分析。电感耦合等离子体质谱议(ICP-MS)具有检测能力高, 速度快,可同时测试多种痕量及超痕量元素。采用ICP-MS对淡水和海水养殖珍珠的微量元素进行测定,并通过数据处理方法分析, 对比。结果表明：(1) 珍珠中含量较高的微量元素种类(Sr, Zn, Ni, Ba, Mn, Cr, Cu, Pb, Ti, Co, Ce, Zr, La, Rb)大致相同,但淡水养殖珍珠的微量元素总量明显少于海水养殖珍珠;(2) 淡水养殖珍珠的微量元素含量较为规律,具有较为固定的含量序列,即Sr>Mn>Ba>Ni>Cr>Pb;而海水养殖珍珠的微量元素含量差异较大,除了各样品都最富集Sr元素外,没有明显的含量顺序;(3) 珍珠中某些微量元素之间存在显著相关性。结论对养殖珍珠的环境指示, 养殖技术, 鉴定,以及综合开发利用具有一定的指导意义。     

参茸黑锡丸中微量元素的测定

参茸黑锡丸是地道的江西传统名方 ,该药在临床上主要用于厥脱治疗 ,主要功能为回阳固脱。文章采用原子吸收法对中成药参茸黑锡丸等 6种中成药中 4种微量元素进行了测定。并将参茸黑锡丸中微量元素与其他 5种中成药中微量元素进行对照研究 ,结果表明 ,参茸黑锡丸中含有丰富的微量元素 ,而有毒的Hg,Cd微量元素含量都较低 ,能保证药品的使用安全     

Compressive energy of ions in ionic crystals

The possibility of writing the repulsive energy in the Born model of binary ionic crystals as a sum of two separate contributions from the two ions has been investigated. Such an approach leads to two identities, one connecting the lattice spacings of a family of ionic crystals and the other connecting their compressibilities. These identities have been tested on the alkali halide crystals over a range of pressures. The agreement is found to be quite satisfactory. Some further predictions with respect to crystals which exist as two polymorphs have also been tested. In all cases, the deviations of the experimental values from the exact identities can be traced to the fact that second neighbour repulsions in the crystals have been neglected. It is hence concluded that individual compressive energies for ions in ionic crystals is a very attractive possibility.     

LO声子色散对激子结合能的影响

本文计及纵光学声子的色散,计算了激子的结合能,发现计及声子色散所导出的激子有效势,对计算激子的结合能有所改进.     

不同海水浓度灌溉菊芋的营养元素测定

利用原子吸收分光光度法分析了不同海水浓度灌溉不同年份采摘的菊芋中多种微量元素的含量。方法灵敏度高,精密度好,相关系数(r)在0.997 1～0.999 7之间。实验中比较其差异性,结果表明：菊芋是典型的高钾低钠食品,其含量K＞Mg＞Na＞Fe＞Ni＞Zn＞Cu＞Mn＞Cd,Pb,Cr含量极少。不同年份和不同海水浓度对其有一定的影响。此法有一定应用价值。     

镍电解液中主要成分和微量成分的ICP－AES测定

本文报告了镍电解中主要成分和微量成分的电感耦合等离子体测定方法，该法简便、快速、准确，可满意地测定试样中Ｆｅ、Ｃｕ、Ｃａ、Ｍｇ、Ｃｏ、Ｎｉ的浓度。     

Correlation between I-Ag distance and ionic conductivity in AgI fast-ion-conducting glasses

A large number of AgI-based fast-ion-conducting glasses have been investigated by K-iodine extended x-ray absorption fine structure spectroscopy (EXAFS) measurements at liquid nitrogen temperature. A general correlation between the I-Ag distance measured by EXAFS and the glass activation energy for dc ionic conductivity has been found out: glasses with longer I-Ag distances display higher ionic conductivity, independently from the chemical composition of their host glassy matrix. This behavior can be related to the progressive increase of the "pathway volume" for ionic conduction.