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.

超高压高温下石墨向金刚石直接转变的EET理论分析

石墨向金刚石在超高压高温下的转变机理经过了数十年的探讨,至今未形成定论。本文根据固体和分子经验电子理论(EET理论),分别计算了静压超高压高温条件下立方合成立方金刚石过程中石墨和金刚石的价电子结构,获得了石墨和金刚石12组不同组合晶面间的价电子密度。结果表明,在超高压高温下其电子密度差均大于10%,说明石墨/金刚石晶面的价电子结构差异太大,不能诱发石墨向立方金刚石的直接转变。分析认为:超高压高温下,石墨先分解出一亚稳相后再转变成立方金刚石结构。

高温高压下cBN单晶转变机理的EET理论分析

使用ab从头算原理计算了六方氮化硼(hBN)和立方氮化硼(cBN)在cBN单晶合成温度和压强下(1800K,5.0GPa)的晶格常数。通过EET理论构建了hBN和cBN的共价电子结构,并计算出九组hBN和cBN单晶的不同低指数晶面之间在高温高压下的相对共价电子密度。根据TFDC理论分析判断,发现hBN的(110)与cBN的(110)、hBN的(100)与cBN的(100)分别连续,两组晶面组合的相对共价电子密度差均小于<10%。这表明:这两组hBN/cBN晶面之间的价电子结构相差不大,可以诱使hBN直接转变为cBN。因此本文认为:从价电子结构的角度分析,高温高压下的cBN单晶极有可能是由hBN直接转变而来的。

稀土低碳钢相变行为的EET理论研究

以添加稀土的Q345B钢为研究对象,运用固体与分子经验电子理论(Empirical Electron Theory,EET),建立了稀土低碳钢中相变行为的价电子结构模型,从电子层次揭示了稀土在低碳钢中的作用机理。理论计算结果表明,随着稀土Ce原子的固溶,原γ-Fe晶胞中Fe原子的混乱状态有所升高,这种较强的γ-Fe-Ce键形成规则排列,晶胞中参与结合的共价电子对数明显增加,高于γ-Fe晶胞的共价电子对数,这使得珠光体转变过程需要更大的过冷度才能完成,也即稀土钢的C-曲线临界温度降低,形成向下拖曳。同时,共价电子对数和相结构因子S的变化也促进了晶粒细化。利用EET理论预测稀土低碳钢相变结果与实测的CCT图结果吻合良好,验证了该方法的有效性和可靠性。

利用经验电子理论(EET)分析Al对Fe-Cr高温合金冲击韧性的影响

采用Thermal calc热力学软件,计算了新型含铝Fe-Cr合金(/%:1.60C、26.00Cr、5.50Al、0.50Ni、0.12Y)的相图,结合X射线衍射分析,确定了该合金的相组成。在此基础上,运用固体与分子经验电子理论(EET),分析了普通高铬铸铁和含铝Fe-Cr合金的价电子结构、共价键键能以及晶格电子数,从电子层面揭示含铝Fe-Cr合金冲击韧性下降的微观机理。结果表明,添加5.50%Al后,Fe-Cr合金中出现了含铝结构单元,这些单元中最强键共价电子对数从0.48640降低为0.450 31,次强键共价电子对数也从0.199 83降低到0.118 88,同时晶格电子数有所减少,从而导致其冲击韧性下降。含5.50%Al的Fe-Cr高温合金冲击韧性的EET预测结果与实测结果吻合良好。

Correlation between valence electronic structure and magnetic properties in RCo_5(R=rare earth) intermetallic compound

The magnetisms of RCo5（R = rare earth） intermetallics are systematically studied with the empirical electron theory of solids and molecules（EET）.The theoretical moments and Curie temperatures agree well with experimental ones.The calculated results show strong correlations between the valence electronic structure and the magnetic properties in RCo5 intermetallic compounds.The moments of RCo5 intermetallics originate mainly from the 3d electrons of Co atoms and 4f electrons of rare earth,and the s electrons also affect the magnetic moments by the hybridization of d and s electrons.It is found that moment of Co atom at 2c site is higher than that at 3g site due to the fact that the bonding effect between R and Co is associated with an electron transformation from 3d electrons into covalence electrons.In the heavy rare-earth-based RCo5 intermetallics,the contribution to magnetic moment originates from the 3d and 4f electrons.The covalence electrons and lattice electrons also affect the Curie temperature,which is proportional to the average moment along the various bonds.

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）.

FeSiBPCu非晶合金磁性的EET理论计算

采用熔体旋淬法制备了(Fe0.76Si0.096B0.084P0.06)100-xCux(x=0,0.1,0.3,0.5)非晶合金,使用X射线衍射仪(XRD)、透射电镜(TEM)和振动样品磁强计(VSM))对其进行表征,结果表明,制备的急冷条带均为非晶态。利用固体与分子经验电子理论,从价电子层次上计算了(Fe0.76Si0.096B0.084P0.06)100-xCux(x=0,0.1,0.3,0.5)非晶合金的价电子结构和磁矩,磁矩的理论计算值163.918、163.692、163.231、162.800 emu/g与实验值160.1、159.0、155.6和153.3 emu/g的误差均小于10%。为新的合金成分设计提供了一种新思路。

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.

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 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.

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.

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。

Al-Ag合金γ相周围无沉淀带形成的机理研究

运用固体经验电子理论(EET),对Al-Ag合金γ相的价电子结构以及γ相与基体的界面能进行了计算。结果表明,沉淀相与基体的界面处能量连续性较差,γ相的表面结合能高于基体的表面结合能,在界面处形成能量势阱。因此结合能大的γ相表面易吸附界面附近基体的Ag原子,引起γ相周围Ag原子的贫乏,出现γ相无沉淀带(PFZ)。

微量铬元素对FeB相价电子结构的影响

进行了铬元素降低硼化物层脆性实验验证 ,用EET(ExperimentalElectronTheory)理论 ,着重分析了微量铬元素对FeB相价电子结构的影响。认为 :铬原子置换FeB相中的Fe原子 ,可改善FeB相空间键络分布不均匀的状况 ,使强键与弱键差值减小 ,提高弱键的键能 ,对其他键也有不同程度的强化作用 。

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。