Electron velocity and momentum density

A null 4-vector ^°, based on Dirac's relativistic electron equation, is shown explicitly for a plane wave and various Coulomb states. This 4-vector constitutes a mechanical model for the electron in those states, and expresses the important spinor quantities represented conventionally byn, f, g, m, j, ,1, ands. The model for a plane wave agrees precisely with the relation between velocity and phase gradient customarily used in quantum theory, but the models for Coulomb states contradict that relation.     

Electronic band structure,stability, structural,and elastic properties of IrTi alloys

The structural properties and mechanical stabilities of B2-IrTi have been investigated using first-principle calculations. The elastic constants calculations indicate that the B2-IrTi is unstable to external strain and the softening of C₁₁−C₁₂ triggers the B2-IrTi (cubic) to L1₀-IrTi (tetragonal) phase transformation. Detailed electronic structure analysis revealed a Jahn–Teller-type band split that could be responsible for elastic softening and structure phase transition. The cubic–tetragonal transition is accompanied by a reduction in the density of states (DOS) at the Fermi level and the d-DOS of Ti at Fermi level plays a decisive role in destabilizing the B2-IrTi phase.     

Electron momentum density and phase transition in SrO

In this article, we present electron momentum density distribution and phase transition in SrO. The experimental values of momentum density have been measured using 5Ci ²⁴¹Am Compton spectrometer and analyzed using theoretical data obtained from the ab-initio linear combination of atomic orbitals method. The first-principles calculations of the total energy of SrO as a function of cell volume have also been carried out for the cubic rocksalt (B1) and cesium chloride (B2) phases. Several structural parameters, i.e. equilibrium lattice constant, transition pressure, bulk modulus, etc. of B1 and B2 phases have been calculated and compared with the previous investigations. We conclude that the stable phase of SrO is B1 and the phase transition from B1 to B2 occurs at 35.8?GPa.     

Electron correlations, spontaneous magnetization and momentum density in quantum dots

The magnetization of quantum dots (QDs) is discussed in terms of a relatively simple but exactly solvable model Hamiltonian. The model predicts oscillations in spin polarization as a function of dot radius for a fixed electron density. These oscillations in magnetization are shown to yield distinct signature in the momentum density of the electron gas, suggesting the usefulness of momentum resolved spectroscopies for investigating the magnetization of dot systems. We also present variational quantum Monte Carlo calculations on a square dot containing 12 electrons in order to gain insight into correlation effects on the interactions between like and unlike spins in a QD.     

He,Ne,Ar,Kr和Xe原子电子的动量密度分布研究

对He,Ne,Ar,Kr和Xe原子体系中电子在动量空间的性质进行了系统的理论计算研究.采用自洽场HFR方法计算了坐标空间He,Ne,Kr和Xe原子体系单电子径向波函数,动量空间的单电子波函数由坐标空间原子体系单电子径向波函数通过运用傅立叶变换计算得到.在冲量近似条件下,进一步计算研究了这些原子的单电子动量密度分布和原子体系总的Compton轮廓.计算结果与已有的实验实验值和其他文献的理论计算结果比较表明,本文计算的结果是准确的.     

Electron momentum density and Compton profile by a semi-empirical approach

Here we propose a semi-empirical approach to describe with good accuracy the electron momentum densities and Compton profiles for a wide range of pure crystalline metals. In the present approach, we use an experimental Compton profile to fit an analytical expression for the momentum densities of the valence electrons. This expression is similar to a Fermi–Dirac distribution function with two parameters, one of which coincides with the ground state kinetic energy of the free-electron gas and the other resembles the electron–electron interaction energy. In the proposed scheme conduction electrons are neither completely free nor completely bound to the atomic nucleus. This procedure allows us to include correlation effects.We tested the approach for all metals with Z=3–50 and showed the results for three representative elements: Li, Be and Al from high-resolution experiments.     

Theoretical investigation of the structural stabilities,elastic properties and band structure characteristics of platinum carbide

Ab initio calculations based on the density functional theory within the full-potential linearized augmented plane wave method were carried out to investigate the structural stabilities of the different crystallographic phases, the pressure-induced phase transition and the electronic properties of the platinum carbide (PtC) compound. The zinc-blende (ZB), rock-salt (RS), cesium chloride (CsCl), wurtzite (WZ), nickel arsenide (NiAs), lead monoxide (PbO) and the tungsten carbide (WC) phases were considered. The exchange and correlation potential was treated by the generalized-gradient approximation using the Perde–Burke–Ernzerhof parameterization. The thermodynamic properties such as variation of the bulk modulus, lattice constant, heat capacity, thermal expansion and Debye temperature versus pressures and temperatures are investigated. The band structure results show the metallic character of the PtC compound in all the considered phases and the present study also shows that the PtC compound crystallizes in the ZB phase at ambient conditions. The theoretical transition pressures from the ZB to RS for the NiAs, PbO and CsCl transformations were also computed.     

Electron momentum density distribution in iridium by Compton scattering technique

The isotropic Compton profile of iridium, measured using 59.54 keVγ-rays, is reported in this paper. The results are compared with the theoretical Compton profiles from APW method with and without incorporating electron correlation effects. It is seen that correlation effects improve the agreement between the experiment and theory. Comparison with the renormalized-free-atom (RFA) model calculations has also been made. Behaviour ofd-band electrons in Ir and some other 5d transition metals is discussed in terms of broadening in their Compton profiles.     

Optical properties and band structure of CdSb

The optical constants of CdSb were determined for photon energies up to 2 eV from reflectivity measurements and by using the Kramers-Kronig dispersion relation. The experimental set-up for the reflectivity measurements is described. Possible locations of the observed direct transitions are found by the application of the selection rules. It is shown how these results, together with some results regarding the transport properties of CdSb, can be used to obtain information about the structure of the valence and conduction bands.     

Electronic band structure,Fermi surface,structural and elastic properties of two polymorphs of MgFeSeO as possible new superconducting systems

By means of DFT-based ab initio calculations, we examine two polymorphs of the newly synthesized 1111-like MgFeSeO as possible new superconducting systems. We have found that the polymorph with blocks [MgO], where Mg atoms are placed in the centers of O₄ tetrahedra, is dynamically unstable unlike the ZrCu-SiAs-type polymorph with oxygen atoms placed in the centers of Mg₄ tetrahedra. The characterization of this material covers the structural, elastic properties, electronic band structure, density of electronic states, and Fermi surface. Our calculations suggest that a high critical temperature for MgFeSeO may be achieved as a result of electron or hole doping through ion substitutions or through creation of lattice vacancies.     

An LCAO band structure and density of states of lead

An LCAO investigation of the electronic structure of lead metal shows that crystal field effects are responsible for the splittings observed, by XPS, in the 6p states.     

Electron spin polarization and conduction band structure of doped ferromagnetic semiconductors

The spin polarization of the conduction electrons of a doped semiconductor (e.g. EuO + x%Gd) is calculated using a moment method together with an alloy analogy. It is shown to be caused by a complicated temperature- and carrier concentration-dependence of the quasiparticle spectrum of the s-f model. Obtained polarization agrees very well with recent photoemission experimental data.     

电子俘获材料SrS:Eu,Sm,Er的光谱特性和光存储特性

提出一种Er3+改进的电子俘获光存储材料SrS∶Eu0.002,Sm0.002,Erx,其中,0≤x≤0.006。通过水热反应,研究了不同退火温度对荧光粉晶相形成的影响,以及不同含量的Er3+对荧光粉的发光性质以及光存储特性的影响。结果表明,Er3+的引入导致荧光增强及光存储特性提高。当Er3+的摩尔分数x=0.003时,荧光强度、光激励发光强度及光存储量出现最大值,分别为不含Er3+时的1.9倍、2倍和3.5倍。同时,Er3+的掺入不改变样品的晶体结构和衰减特性。     

铀的弹性、能带结构和光学常数的第一性原理计算

采用密度泛函理论,赝势平面波方法计算了金属铀a相的晶体结构,弹性常数,体模量,电子能带结构和光学常数(折射率n和消光系数k)等.其中,铀的晶格参数,弹性常数和体模量等与实验及其它第一性原理计算结果十分吻合.计算得到了铀的光学常数,与实验结果作了对比并进行了分析说明.     

Edge-localized-mode--induced transport of impurity density, energy, and momentum

High temporal and spatial resolution measurements of impurity dynamics associated with an edge-localized mode (ELM) indicate that the ELM perturbation consists of two distinct parts: a rapid (< 300 micros) expulsion of impurity density at the time of the instability followed by a slower time scale (< 1 ms) decrease in the ion temperature. While the density perturbation remains nearly constant over a wide range of plasma collisionality, the temperature perturbation decreases as the collisionality increases. Analysis of the radial electric field E(r) evolution indicates that the E(r) well normally present in H-mode plasmas is modified strongly by the ELM and that the size of the temperature perturbation is correlated with the associated change in the E x B shear.     

Theoretical investigations of the optical properties of SrS

A computation of the band structure of SrS is performed self-consistently by the method of linear associated plane waves within the framework of the electron density functional. On the basis of the states density obtained, computations are made of the imaginary part of the dielectric permittivity function in a constant matrix element approximation and with its exact value taken into account. The strong energy dependence of the matrix element and the necessity to take it into account in computations of the optical characteristics of dielectrics are shown.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 79–81, March, 1990.     

层数调控磷烯能带与光学性质的研究

近年来,黑磷作为兼具石墨烯和过渡金属硫化物之长的新型二维材料而倍受关注.本文基于密度泛函理论,研究了不同厚度黑磷的电子结构与光学性质.结果表明,黑磷的性质与其厚度密切相关,可通过厚度调整实现能带与光学性质的可调控性.层间相互作用导致费米能级附近价带和导带的劈裂,是造成黑磷带隙随层数减小的根本原因.黒磷的静态折射率和静态反射率的大小均随层数的增大有增大的趋势,并且各层黑磷的反射峰均位于紫外光波段.黑磷对光的吸收涵盖了可见光到紫外光区域,对光的损失范围小于4eV.本文基于能带图和分波态密度图,从电子跃迁的角度分析了黑磷各项光学性质的变化情况,旨在为黑磷的带隙及光学性质层数可调控性提供理论依据.     

Up-conversion and optical storage properties of SrS: Eu, Sm in PMMA

An erasable and rewritable optical-storage material SrS: Eu,Sm synthesized. Optical emission and excitation spectra of this material were measured. Using the SrS: Eu, Sm-PMMA film, the image-recording experiment was performed.