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In this Brief Report we discuss a solution of the free-particle Schrödinger equation in which the time and space dependence are not separable. The wave function is written as a product of exponential terms, Hermite polynomials, and a phase. The peaks in the wave function decelerate and then accelerate around t=0. We analyze this behavior within both a quantum and a semiclassical regime. We show that the acceleration does not represent true acceleration of the particle but can be related to th...
In this letter we discuss X-ray magnetic dichroism in magnetic materials where an itinerant model of the magnetic behaviour is appropriate. Inspired by progress made in interpreting dichroism spectra in a localized approach, we show that dichroism spectra are an excellent measure of the orbital and spin magnetic moments in itinerant magnets. By performing an energy decomposition of the sum rules we show that the structure found in dichroism spectra reflects the energy dependence of the magnet...
A self-consistent relativistic band-structure calculation on samarium sulphide using the local-densityapproximation is discussed.The LMTO method was used and the bands were calculated for several values of the lattice constant. The results of these calculations showthatalocal-densityfunctionalapproachcandescribethef-d valencetransition.The importance of using a fully relativistic treatment is emphasised.Inboth the high- and low- volume phases SmS shows a band-gap at the Fermi energy. The stru...
Self-consistent, relativistic band structure calculations on samarium sulphide are described. Energy bands were calculated as a function of lattice constant. An f-d valence transition was observed. The importance of using a fully relativistic formalism is discussed. The limitations of using the local density approximation for this type of material are also described.
A wide range of behaviour is observed in uranium materials with stoichiometry UX,.Many compounds of this type are described well by density functional theory, but several are not. The results of fully relativistic self-consistent density functional calculations using the LMTO method are presented for the materials U S , , USn, and URu,. In the light of these results we discuss the applicability of band theory to these materials and indicate how this correlates with the position of the non-ura...
Quantum revivals are now a well-known phenomena within nonrelativistic quantum theory. In this\ud Letter we display the effects of relativity on revivals and quantum carpets. It is generally believed that\ud revivals do not occur within a relativistic regime. Here we show that while this is generally true, it is\ud possible, in principle, to set up wave packets with specific mathematical properties that do exhibit exact\ud revivals within a fully relativistic theory.
The difference in absorption rate of right or left circularly polarized x-rays by magnetic materials is known as magnetic dichroism and is a well established method of investigating the magnetic properties of materials on a microscopic level. In this paper we illustrate this effect with a study of magnetic dichroism in the one-electron atom. The standard relativistic one-electron atom is solved. First-order perturbation theory is used to calculate eigenfunctions in an applied constant magneti...
We have calculated the electronic structure of the high-temperature super- conductors Bi,Sr2Cu06and TI,Ba,CuO,. We find that the T1-0 layers are mainly covalently bonded,whereastheBi-0 layersalsohaveanioniccomponent.Thesematerialshavevery similar crystal structures, but radically different superconducting properties, T , = 12 K and 90 K respectively. We focus on how ‘metallic’ the Bi/T1 layers are and the degree to which the CuO, layers are doped by charge transfer as possible reasons for thi...
The electronic structure of CoTe. NiTe and NiSe has been calculated using the local approximation to density functional theory. The calculations \\ere performed usins the Lwo method. It is argued that the results can be regarded as a first approximation to the electronic structure of the liquids. Bonding and the role of charge transfer are discussed. Resistivit! ratios are calculated on the basis of a simple model and sho\sn to be in excellent agreement uith experiment.
We apply our recent first-principles formalism of magnetic scattering of circularly polarized x rays to a single Cu crystal. We demonstrate the ability of our formalism to interpret the crystalline environment related near-edge fine structure features in the resonant x-ray scattering spectra at the Cu K absorption edge. We find good agreement between the computed and measured diffraction anomalous fine structure features of the x-ray scattering spectra.