Influence of field evaporation on Radial Distribution Functions in Atom Probe Tomography

This paper examines the extraction of structural information in the form of Radial Distribution Functions (RDFs) using Atom Probe Tomography (APT) data. These functions are generated in a highly efficient manner, thus allowing for the analysis of large data sets typical of APT. Experimental RDF calculations were performed for crystalline aluminium and a Mg₆₅Cu₂₅Y₁₀ bulk metallic glass. For the pure aluminium sample, significant pair distance information was extracted, the quality of which was found to vary throughout the data set. Through a novel analysis procedure, the measured total RDF was used to map the local pair distance quality about each reconstructed atom. Surprisingly, the RDF quality maps indicated improved pair distance quality around poles and zone lines. In the case of the metallic glass, however, significant pair correlations were not discernible within the data set, despite short-range ordering being observed using TEM diffraction. The lack of correlations is thought to be associated with a non-uniform ion desorption sequence, as observed in this study. This affects the uniform evaporation assumption that is implicit in current 3D APT reconstruction procedures.     

Determination of the Radial Distribution of Attenuation in Single-Mode Optical Fibers

A new method to determine the radial distribution of attenuation in single-mode optical fibers is proposed. As an example, radiation-induced losses in gamma-irradiated germanosilicate fibers are characterized at 633 nm.     

磷酸二氢铵水溶液构型能和径向分布函数的分子动力学模拟

采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究．磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型．在饱和温度 附近,体系局域粒子数密度有波动．373?400 K的溶液势能增长缓慢表明磷酸二氢铵部分分解．磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变．温度对磷酸二氢根中的氢原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基元产生．     

Radial Distribution Functions for Molecules in the Universal Equation of State Model for Gaseous/Fluid/Condensed Systems

Analytical expressions and a numerical method for calculation of distribution functions of hard spheres gij(r) based on inverting the Laplace transform for functions rgij(r) obtained from the Percus—Yevick equation are obtained. The method for calculation of radial distribution functions is applicable for any distances between hard spheres; it is verified by comparison of numerical results and Monte Carlo simulations. The application of the developed method for calculation of the radial distribution functions of metal atoms is demonstrated. Distribution functions are required to construct a universal theoretical model of equation of state capable of describing both dense multicomponent gas and condensed substances (liquid or solid phases) with high accuracy which is substantially faster than computer experiments (Monte Carlo and molecular dynamics methods).     

Examinations of phase transitions for Nd(Sn,In)3 and Sm(Sn,In)3 compounds by the electrical resistivity studies

Electrical resistivity derivative of NdSn₃, NdIn₃, SmSn₃ and SmIn₃ has been investigated in the vicinity of Néel temperature. Results were compared with available specific heat data, and a quite satisfactory agreement was observed. Both results indicate the existence of additional phase transitions close to T_N. A notable influence of inner strains on the value of the resistivity derivative was observed.     

Binding enthalpies and entropies of neutral Zn,In And Sn In Ge

A statistical thermodynamical model is developed for a doubly ionizable acceptor with excited states in an elemental semiconductor. The special cases of a singly ionizable acceptor, no excited acceptor states and a neutral solute are readily extracted. The equations obtained describe not only the distribution of an acceptor among its various electronic states but also the chemical potentials of the acceptor atom and of the solvent atom. The equations are applied, with and without the excited states included, to obtain about equally good fits to the low-temperature, low carrier concentration Hall data for Zn in Ge. For the low impurity concentrations involved, the excited states are present and so should be included in the analysis. The ability to obtain an equally good fit with the excited states omitted is most likely due to the fact that the concentrations of the major Zn impurity and the Sb counter dopant are not fixed independently of the Hall measurements. The additional flexibility obtained by treating these concentrations as adjustable parameters is sufficient to compensate for the error made in neglecting the excited states. In contrast, the solubilities of the acceptors Zn and In are large enough that the excited states should be pushed out of the band gap. Consequently, the equations are applied without the excited states to the experimental chemical potential-solubility data for Zn, In and Sn in Ge to obtain the Gibbs energy, enthalpy and entropy of binding for the neutral (un-ionized) solute at 950 K. With a solute reference phase consisting of an ideal monatomic gas at 0 K, the entropy of binding is close to that for Ge itself, $\text{14.6 cal}\text{K g}$ atom. This implies that, when they are in the neutral state, these substitutional solute atoms behave very much like the Ge atom itself in contributing to the vibrational spectrum. However, the enthalpy of binding varies significantly and is ?3.8, ?39 and ?65 $\text{kcal}\text{g}$ atom for neutral Zn, neutral In and Sn, respectively, compared to $\text{?84 kcal}\text{g}$ atom for Ge.     

Thermotransport of Ag,In and Sb in liquid Sn

A pseudopotential based model of the electronic contribution to the thermotransport in liquid metal alloys is proposed. The temperature variation of the experimental heat of transport Q¹ allows one to separate the so-called intrinsic and electronic parts of Q¹.     

Theoretical and analytical Radial Distribution Function for non-polar mixtures

The theoretical and analytical Radial Distribution Function (RDF) for non-polar mixtures is presented, and the estimation methods of model parameters (such as the minimum molecular diameter d_ii, mean calibration factor of volume β_V and mean free path of relative motion λ_r,ij) are discussed. The calculated thermodynamic properties for H_e-H₂ fluid mixtures by this RDF fit well with that of MC simulations and classical results from the Yukawa-type EOS, in which the Double Yukawa (DY) potential was used and the quantum effect was considered. Compared with the semi-empirical RDF expressions in references, the advantage of this theoretical and analytical RDF is that it can be used for all kinds of potential functions of non-polar molecules, and it covers a very wide range of temperatures and densities. The extensive practical application of this RDF for chemistry, physics and technology needs further investigation.     

Extension of Compressibility-Route Cubic Equations of State and the Radial Distribution Functions at Contact to Multi-Component Hard-Sphere Mixtures

The equation of state(EOS) for hard-sphere fluid derived from compressibility routes of Percus-Yevick theory(PYC) is extended. The two parameters are determined by fitting well-known virial coefficients of pure fluid.The extended cubic EOS can be directly extended to multi-component mixtures, merely demanding the EOS of mixtures also is cubic and combining two physical conditions for the radial distribution functions at contact(RDFC) of mixtures.The calculated virial coefficients of pure fluid and predicted compressibility factors and RDFC for both pure fluid and mixtures are excellent as compared with the simulation data. The values of RDFC for mixtures with extremely large size ratio 10 are far better than the BGHLL expressions in literature.     

Extension of Compressibility-Route Cubic Equations of State and the Radial Distribution Functions at Contact to Multi-Component Hard-Sphere Mixtures

The equation of state (EOS) for hard-sphere fluid derived from compressibility routes of Percus-Yevick theory (PYC) is extended. The two parameters are determined by fitting well-known virial coefficients of pure fluid. The extended cubic EOS can be directly extended to multi-component mixtures, merely demanding the EOS of mixtures also is cubic and combining two physical conditions for the radial distribution functions at contact (RDFC) of mixtures. The calculated virial coefficients of pure fluid and predicted compressibility factors and RDFC for both pure fluid and mixtures are excellent as compared with the simulation data. The values of RDFC for mixtures with extremely large size ratio 10 are far better than the BGHLL expressions in literature.     

在40MeV/u时112Sn+112Sn和124Sn+124Sn中多重碎裂的同位旋效应

利用同位旋相关的量子分子动力学模型,研究了^112Sn ^112Sn和^124Sn ^124Sn两个反应系统在入射能量E=40MeV/u时的多重碎裂。计算结果与实验值定性符合。观察到了两个反应系统中,中等质量碎片多重性,中子多重性,荷电粒子多重性与轻荷电粒子多重性之间的关联存在着明显的差别。另外,通过与膨胀蒸发源模型及同位旋相关的渗透模型分析结果的比较,发现这种差别主要是由同位旋相关的反应动力学所造成的。     

在40MeV/u时112Sn+112Sn和124Sn+124Sn中多重碎裂的同位旋效应

利用同位旋相关的量子分子动力学模型,研究了112Sn+112Sn和124Sn+124Sn两个反应系统在入射能量E=40MeV/u时的多重碎裂.计算结果能与实验值定性符合.观察到两个反应系统中,中等质量碎片多重性、中子多重性、荷电粒子多重性与轻荷电粒子多重性之间的关联存在着明显的差别.另外,通过与膨胀蒸发源模型及同位旋相关的渗透模型分析结果的比较,发现这种差别主要是由同位旋相关的反应动力学所造成的.     

High-resolution LMN and LMM Auger spectra of Pd,Ag, In,Sn and Sb

Considerable interest in high-resolution Auger spectroscopy of the 4d metals has arisen because of the possibility of treating Auger spectroscopy as an excited state probe in order to extract new information regarding electronic structure. Auger transitions involving only core levels are interesting because current theories of line shapes and energies usually assume that the final core holes are either atomic or quasi-atomic. Comparison of the results of atomic calculations with experimental Auger spectra comprises a crucial test of the atomic theories.We present the results of high-resolution measurements of several high energy LMN and LMM Auger spectra of Pd, Ag, In, Sn and Sb excited with Ti Kα radiation. Assignments of the peaks are based upon energy and intensity considerations. We compare the experimental spectra with the results of atomic transition probability calculations, which indicates the reliability of such calculations as we proceed from open to closed 4d shell metals.     

ICP-AES直接测定海泥中的铅、锡、锌和镉

使用ICP-AES同时测定了海泥样品中的铅、锡、锌、镉。方法加标回收率为95.3%—103.2%,11次测定的RSD(n=11)小于4.59%。方法操作方便,分析速度快,结果准确。     

Continuity Conditions for the Radial Distribution Function of Square-Well Fluids

The continuity properties of the radial distribution function g(r) and its close relative the cavity function y(r) are studied in the context of the Percus–Yevick (PY) integral equation for 3D square-well fluids. The cases corresponding to a well width (–1) equal to a fraction of the diameter of the hard core /m, with m=1, 2, 3, have been considered. In these cases, it is proved that the function y(r) and its first derivative are everywhere continuous, but eventually the derivative of some order becomes discontinuous at the points (n+1)/m, n=0, 1,.... The order of continuity [the highest order derivative of y(r) being continuous at a given point] _n is found to be _nn in the first case (m=1) and _n2n in the other two cases (m=2, 3), for n1. Moreover, derivatives of y(r) up to third order are continuous at r= and r= for =3/2 and =4/3, but only the first derivative is continuous for =2. This can be understood as a nonlinear resonance effect.     

Electronic structure of CeRhX (X = Sn,In)

Electronic structure of the compounds CeRhIn and CeRhSn have been studied by the X-ray photoemission spectroscopy (XPS) and ab initio band structure calculations. CeRhSn shows the non-Fermi liquid characteristics at low temperatures, while CeRhIn exhibits a Fermi-liquid ground state. At ambient temperature the XPS data reveal an intermediate valence state of Ce ions in both systems. The Ce core-level XPS spectra are very similar and indicate the strong coupling of the Ce 4f and the conduction band states (Δ ≈ 100 meV). The valence band spectra we interpret with the help of ab initio calculations as well as using the results for the reference compounds LaRhIn and LaRhSn. The comparative analysis of the theoretical band structures and charge density plots reveal the changes in chemical bonding and the hybridization between the Ce 4f and the other valence states introduced by the replacement of In by Sn atoms. The more covalent character of the chemical bonding in the stannides is in line with the smaller thermal expansion. Finally, for CeRhIn we found a typical temperature dependence of the crystal lattice, while CeRhSn shows distinct anomaly at about 120 K, presumably related to the change in planar Ce–Rh bonds.     

用DV－4光谱仪分析航空结构钢中Pb、Sn、As、Sb、Bi

本文介绍了分析航空结构钢中Ｐｂ、Ｓｎ、Ａｓ、Ｓｂ、Ｂｉ残余元素的一种新的快速方法──发射光谱分析法，找出了最佳分析参数，建立了校准曲线，经精密度和准确度试验后，相对标准偏差为１．２５％－９．１０％，结果令人满意。