金属石墨层间化合物的量子化学和热力学研究

采用量子化学密度泛函B3LYP方法,对碱金属、碱土金属和过渡金属石墨层间化合物(A-GIC,AE-GIC和T-GIC)进行计算.从原子净电荷、Mulliken重叠布居和轨道电子数等角度讨论了A-GIC和AE-GIC的电子结构与成键特性,初步阐明了结构与性能的关系.根据计算结果,结合热力学分析,讨论实验上尚未知的过渡金属石墨层间化合物合成的可能性.     

尾式酪氨酸锌卟啉的合成及其非线性光学和热力学性质研究

报道了一种新型尾式酪氨酸锌卟啉(p-(L-Tyr)NC₂H₄OTPPZn)的合成及表征，围绕该化合物进行了非线性光学及热力学性质研究。样品在激光作用下，在一定波长范围内显示出了非常强烈的反饱和吸收行为。对该化合物与3对氨基酸甲酯客体的轴向配位热力学性质作了研究，从热力学数据和圆二色光谱探讨了与不同客体配位能力的差异。     

有机金属化合物的振动光谱I:环戊二烯夹心化合物的力常数计算

测定了过渡金属环戊二烯夹心化合物的红外与激光拉曼光谱,在此基础上,用G-F矩阵法计算了这类化合物的力常数.讨论了环戊二烯与金属间化学键的性质.     

Fe—C—Sb—Ce,Fe—C—Sb—Y溶液中热力学性质的研究

用金属溶液与高熔点的金属间化合物平衡方法,研究了1300～1500℃含微量氧、硫的Fe-C-Sb-Ce,Fe-C-Sb-Y溶液的热力学性质。经X射线衍射确定平衡产物分别为化合物CeSb、YSb.研究得到反应式CeSb=[Ce]+[Sb]和YSb=[Y]+[Sb]的平衡常数与温度的关系;铈与锑、钇与锑的相互作用系数与温度的关系;CeSb_(s)和YSb_(s)的标准生成自由能与温度的关系。     

铈在钢中固溶度的研究

应用热力学推断了铈在钢中固溶的条件,经与实验对照,两者相符。当钢中的与氧、硫亲合力强的元素含量较高,或铈含量较高,而生成铈铁金属间化合物或铈碳化合物时,便有一定的铈平衡固溶量,并从晶粒中心到边界呈现明显的铈浓度梯度分布。若钢在高温氧化气氛下处理,则其铈铁金属间化合物及铈碳化合物将逐渐被氧化形成CeO_2;当全部生成铈氧化物后,晶粒中便不再存在固溶铈。     

CuSO4—氨化P507—n—C6H14体系平衡常数的计算

用热力学方法研究了酸性磷取剂与金属体系间的平衡计算模型，萃取体系的水相采用Ｐｉｔｚｅｒ半经验公式求算γＣｕ＾２＋，有机相用热力学关系求出了水，正己烷和萃取剂的活度系数，实验结果用Ｓｃｈａｔｃｈａｒｄ－Ｈｉｌｄｅｂｒａｎｄ模型关系，并经回归处理，得到了萃取反应热力学平衡常数及萃合物的活度系数。     

Co-Sm系热力学分析

本文根据Co-Sm系中SmCo_5和Sm_2Co_(17)两个金属间化合物的结构特征,提出了两个相热力学模型,并利用此模型对以SmCo_5为基的固溶体和以θ-Sm_2Co_(17)为基的固溶体之间的相平衡进行了计算,初步表明此模型是基本可行的。     

面心立方C60表面过程的计算机模拟

近年来发现的C60及其金属掺杂化合物形成一个新的材料族，其半导体性质、超导性质及非线性光学性质已受到广泛注意，但目前对这类材料的表面性质尚缺乏研究，我们曾采用参数化的Lenard－Jones6－12模型函数比较不同晶型C6o的相对稳定性　[1]，预测面心立方C60（FccC60）的声子散射频率和态密度[2]，并计算其表面能[3]，取得有意义的结果，表明这一简单模型势能函数是C60分子间有效范德华作用的一种合理抽提．本工作进一步将该势能函数应用于研究fccC60表面吸附分子的迁移机理，并用蒙特卡罗方法模拟fcC（110）及（100）晶面的熔化过程，…     

Fe/Dy非晶多层膜晶化反应的热力学及动力学研究

由Miedema半经验公式计算出了Fe Dy二元系自由能图以揭示Fe Dy非晶多层膜的晶化本质。晶化受热力学和动力学两种因素控制 ,Fe,Dy晶态自由能低于初始非晶态 ,提供了晶化的热力学驱动力 ,而形核势垒及临界晶核尺寸控制了晶化反应的相选择 ,因而中等温度退火时先出现Fe晶粒 ,继而Dy晶粒 ,不出现金属间化合物。     

过渡金属夹心化合物的电子结构

本文利用过渡金属杂硼烷的结构规则,一般性地讨论了过渡金属夹心化合物的电子结构。得到N+1层(N个金属原子)夹心化合物的价成键轨道数为:VBO=6N+3-6N+5,与金属原子和配位环的性质无关。进而,通过用EHMO量子化学方法,对二、三和四层夹心化合物进行模型骨架计算,并结合实际化合物的结构分析,验证和讨论了上述公式的可靠性。     

Low-temperature polyol synthesis of AuCuSn2 and AuNiSn2: using solution chemistry to access ternary intermetallic compounds as nanocrystals

Ternary intermetallic compounds, which possess a wide variety of important properties with both academic and technological relevance, are typically synthesized using traditional high-temperature methods. Here, we demonstrate that the polyol method, which is used extensively to synthesize nanocrystals and nanocrystalline powders of metals and simple binary compounds, serves as an effective low-temperature exploratory medium for synthesizing new ordered ternary intermetallics as nanocrystals. Accordingly, we describe the synthesis and structural characterization of AuCuSn2 and AuNiSn2, which adopt an ordered NiAs-type superstructure that is not observed using equilibrium synthetic methods. AuCuSn2 forms in solution of 120 degrees C as well-formed nanocrystals, and the ordered phase is stable up to 450 degrees C. AuNiSn2 behaves similarly to AuCuSn2.     

Determining a liquidus line under isothermal conditions

A kink in the degree of evaporation-time dependence, due to the accumulation of non-volatile component and the formation of intermetallic compounds, is noted for the evaporation of cadmium from binary alloys with nickel, copper and silver. It is proposed that this feature can be used as a method for determining the liquidus line. Using the existing charts for cadmium-nickel, cadmium, copper, and cadmiumsilver, the method proves to be acceptable for physicochemical research.     

Analytical applications of liquid-liquid phase equilibria: analysis of binary mixtures of chemically similar components

A new, simple and rapid method based on the principle of liquid-liquid phase equilibria has been developed for the analysis of binary mixtures of chemically similar organic compounds. The method does not require elaborate instrumentation and can be used to analyse mixtures of members of homologous series. The application of the method has been illustrated by analysing binary mixtures of n-hexane and n-octane; the maximum uncertainty in this analysis is ~2%.     

Electrodeposition of Bi(x)Fe(1-x) intermetallic compound nanowire arrays and their magnetic properties

There have been few reports on Bi-Fe intermetallic compounds because Bi and Fe are immiscible in the equilibrium states and neither alloy nor intermetallic compound exists in the binary system. In this paper, we show that, by using the nanometer-scale templates based synthesis in conjunction with the electrochemical deposition, it is possible to mix in solid solution elements that are immiscible in traditional fabrication methods. The preparation of Bi-Fe intermetallic compound nanowire arrays was investigated via an electrodeposition route by using a polycarbonate (PC) membrane template. Cyclic voltammetry, potentiostatic transient, and potentiostatic stripping were used to study the formation of Bi(x)Fe(1-x) intermetallic compounds. The compositions of Bi(1-x)Fe(x) intermetallic compound nanowire arrays were sensitive to the bath compositions and the electrodeposition potentials, and the length could be easily adjusted by varying the electrodeposition time. The electrodeposited Bi(1-x)Fe(x) intermetallic compound nanowire arrays had a parallel-to-the-wire easy magnetization. Furthermore, the spin-glass such as behavior and an unusually large characteristic time, which was about 5.26 h, were found in Bi(1-x)Fe(x) intermetallic compound nanowire arrays at room temperature.     

Metallurgy in a beaker: nanoparticle toolkit for the rapid low-temperature solution synthesis of functional multimetallic solid-state materials

Intermetallic compounds and alloys are traditionally synthesized by heating mixtures of metal powders to high temperatures for long periods of time. A low-temperature solution-based alternative has been developed, and this strategy exploits the enhanced reactivity of nanoparticles and the nanometer diffusion distances afforded by binary nanocomposite precursors. Prereduced metal nanoparticles are combined in known ratios, and they form nanomodulated composites that rapidly transform into intermetallics and alloys upon heating at low temperatures. The approach is general in terms of accessible compositions, structures, and morphologies. Multiple compounds in the same binary system can be readily accessed; e.g., AuCu, AuCu3, Au3Cu, and the AuCu-II superlattice are all accessible in the Au-Cu system. This concept can be extended to other binary systems, including the intermetallics FePt3, CoPt, CuPt, and Cu3Pt and the alloys Ag-Pt, Au-Pd, and Ni-Pt. The ternary intermetallic Ag2Pd3S can also be rapidly synthesized at low temperatures from a nanocomposite precursor comprised of Ag2S and Pd nanoparticles. Using this low-temperature solution-based approach, a variety of morphologically diverse nanomaterials are accessible: surface-confined thin films (planar and nonplanar supports), free-standing monoliths, nanomesh materials, inverse opals, and dense gram-scale nanocrystalline powders of intermetallic AuCu. Importantly, the multimetallic materials synthesized using this approach are functional, yielding a room-temperature Fe-Pt ferromagnet, a superconducting sample of Ag2Pd3S (Tc = 1.10 K), and a AuPd4 alloy that selectively catalyzes the formation of H2O2 from H2 and O2. Such flexibility in the synthesis and processing of functional intermetallic and alloy materials is unprecedented.     

A multilayer model for self-propagating high-temperature synthesis of intermetallic compounds

Self-propagating high-temperature synthesis of intermetallic compounds is of wide interest. We consider reactions in a binary system in which the rise and fall of the temperature during the reaction is such that one of the reacting metals melts but not the other. For such a system, using the phase diagram of the binary system, we present a general theory that describes the reaction taking place in a single solid particle of one component surrounded by the melt of the second component. The theory gives us a set of kinetic equations that describe the propagation of the phase interfaces in the solid particle and the change in composition of the melt that surrounds it. In this article, we derive a set of equations for one- and two-layer systems in which each layer is a binary compound in the phase diagram. The system of equations is numerically solved for Al-Ni to illustrate the applicability of the theory. The method presented here is general and, depending on the complexity of the phase diagram, it could be used to obtain similar equations for systems with more layers.     

The generalized standard addition method: intermetallic interferences in anodic stripping voltammetry

A barrier to routine application of anodic stripping voltammetry is the possible formation of intermetallic compounds which can lead to significant errors in the estimated analyte concentrations. As the method of standard additions can correct only for matrix effects, it is powerless to correct for intermetallic interferences which are not matrix effects. By changing the experimental design, the new generalized standard addition method can simultaneously characterize and correct for this type of interference as well as matrix effects expected for real samples. The method is tested on the Cu—Zn—Hg system and error estimates are provided for calculated linear response constants and analyte concentration.     

The μ3 model of acids and bases: extending the Lewis theory to intermetallics

A central challenge in the design of new metallic materials is the elucidation of the chemical factors underlying the structures of intermetallic compounds. Analogies to molecular bonding phenomena, such as the Zintl concept, have proven very productive in approaching this goal. In this Article, we extend a foundational concept of molecular chemistry to intermetallics: the Lewis theory of acids and bases. The connection is developed through the method of moments, as applied to DFT-calibrated Hückel calculations. We begin by illustrating that the third and fourth moments (μ(3) and μ(4)) of the electronic density of states (DOS) distribution tune the properties of a pseudogap. μ(3) controls the balance of states above and below the DOS minimum, with μ(4) then determining the minimum's depth. In this way, μ(3) predicts an ideal occupancy for the DOS distribution. The μ(3)-ideal electron count is used to forge a link between the reactivity of transition metals toward intermetallic phase formation, and that of Lewis acids and bases toward adduct formation. This is accomplished through a moments-based definition of acidity which classifies systems that are electron-poor relative to the μ(3)-ideal as μ(3)-acidic, and those that are electron-rich as μ(3)-basic. The reaction of μ(3) acids and bases, whether in the formation of a Lewis acid/base adduct or an intermetallic phase, tends to neutralize the μ(3) acidity or basicity of the reactants. This μ(3)-neutralization is traced to the influence of electronegativity differences at heteroatomic contacts on the projected DOS curves of the atoms involved. The role of μ(3)-acid/base interactions in intermetallic phases is demonstrated through the examination of 23 binary phases forming between 3d metals, the stability range of the CsCl type, and structural trends within the Ti-Ni system.     

Assessment of Phase Composition of Electrolytic Deposits by Stripping Voltammetry

This paper describes the method of assessing the composition of the intermetallic compounds in nanoscale electrolytic deposits. The formula was developed for calculating the deflection potential in the case of selective electrooxidation electronegative component of the alloy composition. The processes of electro binary electrolytic precipitation in mercury-rhodium chloride electrolyte by anodic stripping voltammetry were studied. It was established that an electrolytic precipitate contains rhodium, mercury and rhodium IC with mercury composition Hg₅Rh.     

Thermodynamics and defect structure of intermetallic phases with the B2 (CsCl) structure

Available theoretical models that describe the thermodynamic properties and the defect structures of intermetallic phases with the B2 structure are reviewed. The experimental methods for the determination of the Gibbs energy of alloys are briefly discussed and a summary of experimental data of lattice parameters, densities, activities, and enthalpies for nearly 30 B2 phases is given. It is shown that the data can be expressed in terms of a few simple model parameters. The importance of theoretical models for an understanding of the structural stability of intermetallic phases and for the evaluation and eventual prediction of binary and ternary phase diagrams is discussed.