Differences of grain-refining effect of Sc and Ti additions in aluminum by empirical electron theory analysis

The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.

A Valence Electron Structure Criterion of Ionic Conductivity of Sr- and Mg-doped LaGaO_3 Ceramics

The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules （EET）. A criterion for the ionic conductivity was proposed, i.e. the 1/（nAnB） increases with increasing the ionic conductivity when x or y〈20% （in molar fraction）.

Theoretical analysis of alloy multiplying factor by the empirical electron theory of solids and molecules

By introducing the distribution probability of structural units in austenite contain- ing alloying elements and considering its effects on phase transformation, this paper establishes a calculation model of distribution probability of structural units. A new valence electron structure (VES) parameter-transformation effect coefficient of alloying elements (HL), is defined and then studied both theoretically and ex- perimentally. The relationship between the parameter HL and the multiplying factor (the quenching capability factor) of alloying elements is studied. The results indi- cate that the two parameters (HL and the quenching capability factor) have the same variation characteristic and substance feature. Therefore, the multiplying factor virtually expresses the relative quantity of structural units in the alloying elements-containing austenite.

THE CALCULATION OF THE COHESIVE ENERGY OFГPHASE IN THE TRANSITIONAL LAYER FE ZN OF HEAT GALVANIZED SHEET USED IN CARS

hethesisanalysesthevalenceelectronstructuresof phase Γin Fe Zn transitionallayerof heat galvanized sheet used in cars by applying the Empirical Electron Theory of Solids andMolecules, and calculatesthebond energy ofthe major bondsand cohesiveenergy ofcrystals,from which we draw theconclusion:sincecrystal has alargercohesiveenergy, it has higherhardness, butsinceitsbondenergyisratherlow ,itiseasytobreak under pressurefrom out side, and thecrackiseasytocome up andspreadin phase Γ.

Effect of Sm doping into CuInTe_(2) on cohesive energy before and after light absorption

The effects of Sm doping into CuInTe_(2) chalcopyrite on the cohesive energy before and after light absorption are systematically investigated by the empirical electron theory(EET) of solids and molecules.The results show that the static energy of CuIn_(1-x)Sm_(x)Te_(2) decreases with Sm content increasing due to the valence electronic structure modulated by doping Sm into CuIn_(1-x)Sm_(x)Te_(2).The calculated optical absorption transition energy from the static state to the excited energy level in CuIn_(1-x)Sm_(x)Te_(2) accords well with the experimental absorption bandgap of CuIn_(1-x)Sm_(x)Te_(2).Moreover,it is found that the energy bandgap of CuIn_(1-x)Sm_(x)Te_(2) is significantly widened with Sm content increasing due to its special valent electron structure,which is favorable for enhancing the light absorption in a wider range and also for the potential applications in solar cells.

Valence electron structure and bonding features of RuB2 and OSB2: The empirical electron theory calculations

The valence electron structure (VES) of RuB2 and OsB2 were calculated by the empirical electron theory (EET) of solids and molecules and compared with the results derived from the first-principles calculations. The distributions of covalent electrons in different bonds indicate that B-B and B-Me have remarkably covalent bonding characters. Lattice electrons cruising around Me-Me layers are found to have great influences on electronic conductivity and high temperature plasticity. The ultra-high values of elastic constant Cn in the two compounds originate from close-packed covalent bonding along the c axis. Uneven bond strengths and distributions of covalent bonds, especially for B-Afe bonds, yield significant anisotropy. Low ratios of lattice electrons to covalent electrons suggest the intrinsic embrittlement in crystals. The fact that the calculated cohesive energies well agree with experimental results demonstrates the good suitability of the EET calculations in estimating cohesive energy for transition-metal borides.

EET理论在超硬材料相变机理研究中的应用

近年来,固体与分子经验电子理论(EET理论)不断完善和发展,并广泛应用于金属及其合金、陶瓷材料等研究领域,尤其是在材料相变机理研究方面取得了一定进展。主要归纳了金刚石单晶、立方氮化硼单晶相变机理的研究进展;提出了用基于EET理论构建的EET-TFDC理论模型来分析单晶高温高压相变机理的研究思路;介绍了EET理论在金刚石单晶、立方氮化硼单晶等超硬材料合成研究过程中的研究现状;展望了EET理论的研究前景。

RAlX系列化合物的价电子结构、结合能和磁矩

针对RAlX(R=La,Ce,Pr;X=Ge,Si)系列化合物,基于固体与分子经验电子理论(EET)构建含4f电子的稀土元素Ce和Pr的杂化表。对EET理论中的K公式进行适应性修正,用修改后的公式计算单质稀土Ce和Pr的内聚能、熔点和磁矩等性能,计算结果与试验结果相符,验证了杂化表的可靠性。用新的杂化表计算Weyl半金属RAlX(R=La,Ce,Pr;X=Ge,Si)的价电子结构(VES)、结合能与磁矩,计算得到的键长和磁矩与试验结果基本一致。结果表明:RAlX化合物的VES与晶体结构、结合能和磁矩有很强的相关性。

Valence electron structure of the(ZrTi)B_2 solid solutions calculated by the three models

The Zr-rich(Zr0.8Ti0.2)B2 and the Ti-rich(Ti0.8Zr0.2)B2 solid solutions are formed when TiB2 and ZrB2 are hot-pressed.To forecast the properties of the two solid solutions,their valence electron structure was analyzed based on the empirical electron theory(EET) of solids and molecules.We used three different models,the average atom model,the average cell model and the real cell model,and compared with the calculation results from the three models.In the real cell model,the lattice constants of the solid solu-tions were supposed to be changed or unchanged.The results showed that different models could only result in slight change in the hybridization levels of the metal atoms in the two solid solutions and little difference between the calculation values.However,they can not change the variant trend of the va-lence electron structure nor the properties of the solid solutions.Thus,the three models and the methods are appropriate and the calculation results are reasonable and consistent.

Valence electronic structure of tantalum carbide and nitride

The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.

Hardness estimation for covalent crystals using Empirical Electron Theory

Covalent electrons substantially determine the intrinsic hardness of inorganic crystals. A hardness model is presented on the basis of the Empirical Electron Theory generated from Pauling’s covalent bond length equation and the bond length difference method. The calculated hardness values of inorganic crystals are in good agreement with experimental and other theoretical values. Covalent bond energy with polarity correction can be used as an intrinsic indicator linking microscopic electronic structure to macroscopic hardness. A simple mathematical processing of bond energy is performed to extend the model to multi-bonding or multi-component systems. It is also found that spatial distribution of covalent bonds has a great influence on the hardness of inorganic crystals.

金刚石单晶解理断裂的研究

本文通过实验观察和理论计算研究了金刚石单晶解理断裂现象。金刚石单晶晶面上实际的价电子密度并非简单的正比于原子密度。(110)晶面上原子分布不均匀。(110)晶面BQKJB区域内原子分布较少,原子密度低于其它晶面。(111)晶面的价电子键络分布均匀,且实际发生作用的价电子密度最大。计算和分析结果表明,金刚石单晶(111)晶面的有效价电子密度为46.212 nm^(-2),明显高于(110)晶面的38.542 nm^(-2),成为有效原子密排面。当金刚石受到外力作用时,(111)面间较弱的键相对更容易断裂,因而导致沿(111)面产生解理。这与实验观察结果相吻合。

Co,Mn元素在LaNi_5储氢合金中的作用机理

利用固体与分子经验电子理论（EET）计算了LaNi5合金的价电子结构和Co、Mn原子替代LSNi5中部分Ni原子后所形成的各种晶胞情况下连接上下两层原子的主要键的键能。Mn原子替代Ni2原子后上述键能增大，Co原子无论替代Ni1或Ni2都能使相关键能增加，两种原子同时替代，其键能增加更明显。可知：Co和Mn是通过增大连接上下两层原子的主要键的键能达到强化合金、延缓合金粉化，从而提高LaNi5合金的循环寿命。

余氏理论在液态合金结构研究中的应用

本文介绍了余氏理论的基本思想及其在固态和液态合金研究中的应用 ,运用余氏理论这一新的理论工具 ,可以使对合金熔体的研究深入到电子结构层次。

Fe-25Al铝化物的电子结构及其本质脆性

铁铝金属间化合物是一类具有良好应用前景的新型材料 ,但室温脆性影响了其进一步应用。本文基于Fe 2 5Al各种物相的晶体结构和实际原子占位 ,运用固体与分子经验电子理论 (EET)建立起Fe 2 5Al各相的价电子结构。通过比较不同相结构的价电子结构参数 ,对Fe3Al的室温脆性进行了阐述。认为较少的晶格电子、键络分布不均匀使Fe3Al具有本质脆性 ,添加固溶组元可以改变价电子结构参数从而改善强度和韧性。

Zr元素对纯铝细化机理的电子理论研究

基于固体与分子经验电子理论(EET),计算了Al-Zr合金熔体中相及相界面的价电子结构,获得了表征合金性能关系的价电子结构参数统计值,并利用这些参数讨论了Zr对纯铝晶粒细化的机理。结果表明:Zr对纯铝的细化机理可以追溯到熔体中Al3Zr与α-Al相晶面间的界面共价电子密度差的统计值Δρ′,即Δρ′<10%且Δρ′值越小,合金中的异质形核效应越好,晶粒细化效果越好。Δρ′值小(2.789 04%)的Al-Al原子团簇能较容易地被异质形核核心(Al_3Zr晶体)吸附,促进异质形核及晶粒细化作用;而Δρ′值大(15.698 70%)的Al-Zr原子团簇容易从异质晶核上脱离,削弱异质形核及晶粒细化效应。

ZrC1-xNx固溶体的价电子结构与性能

为了预测ZrC1-xNx固溶体的性能,根据固体与分子经验电子理论(EET),对该固溶体相进行了价电子结构分析;采用键距差(BLD)方法,计算了固溶体相中的最强键共价电子数、共价键电子数百分比、最强键键能、熔点等,并分别与ZrC、ZrN基体的价电子结构进行比较。结果表明,ZrC与ZrN相互溶入后,非金属原子的杂阶没有变化,但ZrC1-xNx固溶体中Zr原子的杂阶、最强键上共价电子数、共价键电子数百分比、最强键键能以及熔点均随x值变化而变化。随着x值的增加,Zr原子的杂阶从B11上升到B13,最强键上共价键数、最强键键能、熔点逐渐下降,而共价键数百分比逐渐上升,表明固溶体硬度、韧性、结合能、熔点、导电性能逐渐减小,而强度却逐渐增加。

无序化对有序铁铝金属间化合物磁性的影响

在平衡态时,化学计量比成份Fe3Al具有D03超结构,并表现出铁磁性,平均每个Fe原子的磁矩是1.7μB,而具有B2超结构的FeAl却是无磁的。利用快速凝固、冷加工处理、溅射和械合金化等非平衡加工技术可以使D03-Fe3Al和B2-FeAl等有序铁铝金属间化合物相无序化。本文利用固体与分子经验电子理论(EET)和Jaccarino-Walker模型对铁铝金属间化合物的磁性进行了计算,研究了无序化对Fe-Al有序相磁性的影响。结果表明:完全无序的Fe75Al25和Fe50Al50,每个Fe原子的平均磁矩分别是2.01μB、1.41μB,铁铝金属间化合物的磁性可以通过无序化提高。

HfC_(1-x)N_x固溶体的价电子结构与性能

为了预测HfC1-xNx固溶体的性能,根据固体与分子经验电子理论(EET),对这类固溶体相进行了价电子结构分析,并分别与HfC,HfN基体进行比较。结果表明,HfC与HfN相互溶入后,非金属原子的杂阶保持不变,而Hf原子的杂阶从B11逐渐上升到B16;随着x值的增加,最强键上共价电子数、最强键键能、熔点都是逐渐下降,而共价电子总数百分比逐渐上升,表明固溶体的硬度、韧性、结合能、熔点逐渐减小,而强度却增加。

HfC+4TaC固溶体的价电子结构与性能

HfC与TaC在热压过程中易生成HfC+4TaC固溶体,为了预报该固溶体的宏观性能,采用固体与分子经验电子理论(EET),对其价电子结构进行分析,并与TaC、HfC基体进行比较。结果表明,在4TaC+HfC固溶体中,Ta的杂阶保持不变,而Hf、C原子的杂阶略有变化;在4HfC+TaC固溶体中,Hf、C原子的杂阶保持不变,而Ta原子的杂阶剧烈变化。2种固溶体的价电子结构与宏观性能均在HfC与TaC基体之间,并分别接近对应的基体。4种材料的硬度、强度、结合能、熔点排序从低到高依次为HfC、4HfC+TaC、4TaC+HfC、TaC。从能量与熔点角度分析,HfC与TaC接触时容易生成4TaC+HfC固溶体,而4HfC+TaC固溶体就难以生成。