金属中f电子局域磁矩及其退局域化的一个模型(Ⅰ)

本文提出了一个模型,其中f电子束缚在费密面附近的一个窄带内,s-p-d电子是自由的,还考虑了它们之间的杂化。数值计算的结果表明f电子在退局域化过程中有一定的稳定性,温度和杂化对之有明显的影响。文中给出了不同参数空间的相图。最后对稀土变价现象进行了定性讨论。 关键词：     

稀土元素Ce的特性与4f电子局域磁矩

本文考虑到电声子相互作用以及4f电子与传导电子相互作用的贡献,对稀土Ce中伴随γ-α相变时所发生的变价现象与磁性等物理特性的关系作了研究,分析了当温度、压强、化合价等变化时稀土金属中的电子行为。     

铈原子基态的理论研究

在有心力场近似和组态相互作用理论框架下,通过对电子波函数、各壳 层上电子的束缚能、半径、总束缚能的分析和计算,研究了Ce原子的可能的基组态及其基态 时的原子态。研究结果表明：基组态为4f5d,基态原子态为1G4。     

离化态原子的激发态结构

本文根据相对论性自洽场理论,计算了原子序数从2到95的各种离化态原子激发态能级,从而总结了s,p,d,f和g通道的量子数亏损。阐明了量子数亏损随着原子序、电离度(或电子占有数)和电子轨道能量变化的规律。在此基础上可以建立离化态原子激发态量子数亏损数据库。 关键词：     

Xe原子的等核及等电子系列离子径向波函数的性态研究

基于相对论多组态Dirac-Fock方法(MCDF方法),详细研究了Xe及类Xe离子的束缚和连续的f轨道波函数的性态,分析了沿等核系列和等电子系列f轨道径向波函数的塌缩现象.在此基础上,进一步讨论了轨道波函数的塌缩导致的强弛豫效应及其对类Xe离子的4d10-4d94f跃迁能和振子强度的影响.     

对元素基态电子组态表中几个“特殊”组态的解释

在Pauli不相容原理和能量最低原理的限制下,处于基态时原子中的电子按照 1s,2s,2 p, 3s,3 p,4 s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d的次序[1]填充,得出原子基态时的电子组态.但是,在元素基态电子组态表[2]中,有十九个“例外”,形成“特殊”的电子组态.其原因需要研究影响ns,(n—1)d,(n—2)f壳层能量的因素《特别是n很大时》. 量子力学中,作为中心力场近似的 Hartree-Fork自洽场方法,给出了多电子原子的能量公式[3] 式中,第一项是单电子原子实的能量(忽略了与所有其他别的电子的相互作用);第二项是两电子相互作用的库仑能,它表示电子密…     

类铜Au50+离子电子碰撞激发特性的研究

利用全相对论扭曲波（RDW）方法,系统计算了类铜Au50+离子的外壳层电子4s激发到4l 、5l （ l= s、p、d、f,除去4s-4s ）和内壳层电子3l （l = s、p、d）激发到4l 、5l （l = s、p、d、f）的碰撞激发截面,研究了在不同入射电子能量下截面的变化规律,给出了3d-4f 和3d-5f 精细结构能级的碰撞激发截面。部分计算结果与其它理论及最新实验结果进行了比较,取得了很好的一致性。     

类锌Au~(49+)离子电子碰撞激发速率系数的研究

利用全相对论扭曲波方法和研究电子碰撞激发过程的计算程序REIE06系统计算了类锌Au~(49+)离子从基态(3s~23p~63d~(10)4s~2)的4s、3d、3p和3s电子激发到4 l(l=p、d、f)和5 l(l=s、p、d、f)的碰撞激发强度,研究了在不同入射电子能量下碰撞强度的变化规律,通过对类锌Au~(49+)离子涉及金激光等离子体M带谱,3d→4f和3d→5f电子碰撞激发速率的计算,分析了等离子体中电子温度对碰撞过程的影响.部分计算结果与其它理论及实验结果进行了比较,取得了很好的一致性.     

类Li钙离子精细结构能级和软X射线光谱的理论计算

用多组态HFR方法计算了类Li等电子序列钙(Ca,Z=20)离子1s~2nl(n=2～6,l=0～5)组态的所有能级和电偶极跃迁的软X射线光谱,其中4f→3d,5f→3d及5d→3p、4d→3p由于其下能级跃迁速率较大,容易形成粒子数反转因而可作为激光跃迁,5f→3d、6f→3d跃迁已处于“水窗”波段,而4f→3d的激光跃迁(5.77nm)已为我们最近的实验所证实.并将我们的计算结果与其它理论计算和实验数据进行了比较.     

局域密度泛函法比较研究钕铀的电子结构

镧系元素随着原子序数的增加在填充内部的4f电子壳层时，由于在同-4f壳层中的一个电子被另一个电子的屏蔽是不完全的，因此，作用在每个4f电子的有效核电荷是随原子序数的增大而增大，从而引起4f壳层及半径随原子序数的增大而收缩，导致了原子半径在总趋势上有所缩小的现象（从镧到镥总共缩小了0．11pm）。这个现象同样存在于锕系元素中。尽管镧系元素原子半径的缩小幅度远远小于非过渡元素，但它的影响很大。由于镧系收缩的存在，使镧系后面的各过渡元素的原子半径相应缩小，致使同一副族的第五、六周期过渡元素的原子半径非常接近。     

Analysis of the valence electronic structures and calculation of the physical properties of Fe,Co, and Ni

The valence electronic structures of Fe, Co and Ni have been investigated with Empirical Electron Theory of Solids and Molecules. The magnetic moments, Curie temperature, cohesive energy and melting point have been calculated according to the valence electronic structure. These calculations fit the experimental data very well. Based on the calculations, the magnetic moments are proportional to the number of 3d magnetic electrons. Curie temperatures are related to the magnetic electrons and the bond lengths between magnetic atoms. Cohesive energies increase with the increase of the number of covalent electrons, and the decrease of the number of magnetic and dumb pair electrons. The melting point is mainly related to the number of covalent electron pairs distributed in the strongest bond. The contribution from the lattice electrons is very small, the dumb pair electrons weaken the melting point; however, the contribution to melting point of the magnetic electrons can be neglected. It reveals that the magnetic and thermal properties are closely related to the valence electronic structures, and the changes or transitions between the electrons obviously affect the physical properties. Supported by the National High Technology Development Program of China (Grant No. 2007AA03Z458)     

稀土元素的价电子结构和熔点、结合能的关联性

稀土是重要的战略物资资源,有一些已形成产业,在永磁、发光、催化和储氢等方面有着重要的作用. 对稀土及其化合物的研究一直是国内外研究的热点.对稀土原子结构和价电子结构的研究有助于对其的更深刻的理解. 依据固体与分子经验电子理论,对镧系稀土和Sc, Y的价电子结构进行系统地研究, 并以此为基础,对它们的熔点和结合能做进一步分析,分析结果和实验值相符. 研究结果表明:稀土金属的结构与晶格电子和共价电子密切相关,随着晶格电子向共价电子的转换, 稀土金属的熔点趋于增加.稀土的价态变化也是影响电子分布和性能的主因, 如: Sm和Eu的熔点与电子结构的关系不同于其他稀土,外壳层的共价电子之间的转化是其熔点与其他元素之间差别较大的主要原因.稀土的4f电子对结合能的影响大,这是源于其4f电子引发的收缩效应. 此结果揭示了决定稀土熔点和结合能的主要因素是稀土的价电子结构的变化.     

Spin-exchange collisions of submerged shell atoms below 1 Kelvin

Angular momentum changing collisions can be suppressed in atoms whose valence electrons are submerged beneath filled shells of higher principle quantum number. To determine whether spin-exchange collisions are suppressed in these "submerged shell" atoms, we measured collisional rates for six hyperfine states of Mn at T < 1 K. Although the 3d valence electrons in Mn are submerged beneath a filled 4s orbital, we find spin-exchange rate coefficients similar to Na and H (both nonsubmerged shell atoms).     

Optical conductivity of CePd3, YPd3 and PrPd3

The optical conductivity of intermediate valence CePd₃ at 300 K exhibits a maximum near 16 meV, which is absent in the reference materials YPd₃ and PrPd₃. Using a modified Drude model with a memory function ansatz this anomaly has been identified as a resonant electron-electron scattering process of conduction electrons at the localized 4f states near the Fermi level E_F. The model fit gives estimates of the width of the 4f states, of their separation from E_F and of the f-d hybridization energy. Intra-4f transitions of CePd₃ are stronger compared to those of PrPd₃ due to the stronger f-d hybirdization. 4d→4f transition energies of CePd₃ are reduced due to an electron-hole Coulomb binding energy.     

Correlation between electronic structure and energy band in Eu-doped CuInTe_2 semiconductor compound with chalcopyrite structure

The Eu-doped Cu(In, Eu)Te_2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe_2. In this paper, the Eu-doped CuInTe_2(CuIn_(1-x)Eu_xTe_2, x = 0, 0.1, 0.2, 0.3) are studied systemically based on the empirical electron theory(EET). The studies cover crystal structures, bonding regularities, cohesive energies, energy levels,and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe_2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe_2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn_(1-x)Eu_xTe_2, the number of valence electrons changes regularly with increasing Eu content,and the calculated band gap E_g also increases, which implies that the optical properties of Eu-doped CuIn_(1-x)Eu_xTe_2 are improved.     

等价电子数组元Heusler合金Fe_2RuSi中的原子占位

对等价电子数组元Heusler合金Fe_2RuSi的原子占位、电子结构与磁性进行了理论与实验研究.第一性原理计算表明,虽然Fe_2RuSi中Fe,Ru均有8个价电子,但是Ru仍表现出强烈的占据A,C晶位倾向.基态总能最低的是Fe与Ru分别占据A,C晶位的XA结构,次低的是Fe,Ru在A,C位混乱占位的L2_1B结构,且两者能量差很小.这说明决定Heusler合金中过渡族原子占位的因素除价电子数以外还可能有原子半径和共价杂化作用等.态密度和差分电荷密度计算表明Heusler合金中主族元素与最近邻过渡族元素之间的p-d共价杂化对Heusler合金的占位有明显影响,在XA结构中Ru与Si和Fe(B)之间都存在明显的杂化作用,而在高能的L2_1结构中,Si与最近邻的Fe杂化作用相当弱.XRD测试表明在室温Fe_2RuSi存在A,C位之间的Fe-Ru反占位,形成了能量次高的L21B结构,这主要来自于混合熵对自由能的贡献及其引起的原子自发混乱占位.在5 K下Fe_2RuSi的饱和磁矩为4.87μB/f.u.,与计算值符合得相当好.     

First principles study on the charge density and the bulk modulus of the transition metals and their carbides and nitrides

A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.     

Investigation of the formation of the electron structure of metallocarbonic nanoforms

Model samples of nanostructures are synthesized with the use of transition metals, with a different number of d electrons and sp elements of groups II and III with a different number of valence p electrons, as modifiers. The activity of nanostructure synthesis is investigated depending on the addition of sp elements. A procedure is developed for determining the atomic magnetic moment of the d metals and the change in the distances between atoms of the metal and the sp element via the parameters of the X-ray photoelectron spectrum of transition metals, which allows the degree of hybridization of valence electrons in the chemical bond of adjacent atoms (Me-X) to be determined. As a result of the investigation the laws of nanoform growth are found which facilitate the development of new directions in the synthesis of nanostructures with unique properties.     

Photoelectron spectroscopy

The energy spectra of photoejected electrons provides a direct method for determining the electronic binding energies in atoms, molecules and solids. The binding energies may be used to identify a particular atom in a molecule or solid and, as well, to indicate from which orbital the electrons were removed. The relative intensities of peaks in the photoelectron spectrum reveal the nature of the chemical bond in a molecule and are a measure of the relative transition probabilities for ionization to a particular state. The effects of autoionization and angular distribution are discussed, and some applications are given.     

Yb2.75C60同步辐射光电子能谱

在超高真空系统中制备了Yb275C60薄膜.对样品进行了同步辐射光电子能谱研究.在费米能级以下约5 eV范围内的谱数据由Yb275C60价带（C60分子轨道LUMO，HOMO和HOMO 1导出的能带）和芯态（Yb 4f7/2，4f5/2）能级构成.用紫外能区不同能量的入射光子，用C 2p和Yb 4f光电离截面随光子能量的不同变化规律，通过定量拟合，得到了对谱线有贡献的上述各个组分的峰位、峰宽和强度.结果表明，光子能量高于约300 eV时，芯态4f的贡献使得实验结果远远偏离价带的本征态密度分布.因此，研究Yb275C60价态时，应使用能量低于300 eV的光子.对实验和拟合结果分析，发现了类似纯C60的光电离截面振荡现象.振荡幅度相对于纯C60较小，反映了化合物中C60分子的化学环境对光电离截面振荡现象起着不可忽略的作用. 关键词： Yb275C60 同步辐射光电子能谱 光电离截面振荡