Molecular Compton profiles from SCF-MO wavefunctions

This paper considers the dependence of Compton profiles calculated from molecular wavefunctions on the atomic basis set used. For fluoromethane there is no significant difference between profiles calculated with a Slater minimal basis set and with STO-3G, STO-4G and STO-5G sets. A Slater double-zeta set and Dunning's gaussian basis give essentially the same profile and the addition of polarization functions to the Dunning basis has little effect. For methanol, methylamine and ethane there is a significant difference between the STO-3G profiles and those calculated from extended basis sets but again the addition of polarization functions has little effect. The use of Dunning's basis would seem to be adequate for Compton profile calculations for molecules of medium size. As one goes along the series from ethane to fluoromethane the Compton profile becomes broader.     

Derivation of the radial distribution function from experimental Compton profiles

The analysis of experimental Compton profiles in position rather than momentum space provides a useful method of interpreting Compton data. A density matrix approach is employed to establish the relationship between the Compton profile J(p), and the Fourier transform of the momentum density B(r), and, for a homogeneous system, the radial distribution function g(r). An earlier Compton profile measurement on sodium provides the data for a demonstration of the long range charge correlations in a metal, in analogy with the Friedel oscillations in a screening charge.     

Fermi surface parameters from the Fourier analysis of Compton profiles

A new approach to the analysis and interpretation of Compton profiles, based on the properties of the Fourier transform of the profiles, is presented. The method is applied to the determination of Fermi momenta for some simple metals. The remarkable precision of the results obtained in this way illustrates both the power of the technique and also the manner in which this approach enables one to circumvent some major problems inherent in the usual analysis of Compton data.     

New reconstruction method of electron momentum densities from Compton profiles

Recent advances in Compton scattering experiments have led to renewed interest in reconstructing three-dimensional electron momentum densities from Compton profiles. We present a new reconstruction method based on the inversion of the Radon transform in terms of spherical harmonics and Jacobi polynomials. This technique is demonstrated on model projections having the hexagonal symmetry. Reconstructed densities, being in very good agreement with the model ones, are a very good performance of this new algorithm.     

Fourier transformed Compton profiles of semiconductors

The Fourier transformed Compton profiles of several semiconductors are calculated by using a set of realistic Wannier functions. The results obtained in silicon, where experimental information exists, are used to test the one-electron approximation. The study of a series of semiconductors shows the effect of their electronic structure on the Compton scattering.     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法。基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况。通过与文献结果的比较,验证了本文计算方法和结论的可靠性。     

Compton profiles of trigonal and amorphous selenium

Compton profiles of trigonal and amorphous Selenium were measured with ²⁴¹Am γ-radiation using two crystalline and amorphous samples of identical geometric dimensions. As a result the difference profiles of amorphous and polycrystalline Se are reported and discussed. The valence electron Compton profile of the polycrystalline phase is compared to SCOPW-calculations by Krusius.     

Compton profiles of multiply ionized oxygen atoms

We have calculated Compton profiles of multiply ionized oxygen atoms with electronic configurations 1s^m2sⁿ2p^q, m=1−2,n=0−2,q=0−4. The values of the Compton profiles from the present calculation can be used to determine the doubly differential electron production cross sections in recent ion-atom collision experiments with oxygen ions in the rest frame of the target atoms. The calculations have been performed in impulse approximation using numerical Hartree-Fock wave functions. Compton profiles of neutral oxygen atoms, available in the literature, are in excellent agreement with the present calculation. The variation of Compton profile with the degree of ionization is investigated.     

原子康普顿轮廓的解析计算

利用变分原理和冲量近似,给出了原子康普顿轮廓的解析计算方法 .基于该方法具体导出了第一和第二周期元素各轨道电子的康普顿轮廓解析表达式,并绘制了各轨道电子的康普顿轮廓在Q=0-4范围内的变化情况.通过与文献结果的比较,验证了本文计算方法和结论的可靠性.     

Atomic Compton profiles within different exchange-only theories

The impulse Compton Profiles (CPs) J(q) and the expectation values for some inert gas atoms (He-Kr) are computed and compared within the Harbola-Sahni (HS), Hartree-Fock (HF) theories and a Self-Interaction-Corrected (SIC) density functional model. The Compton profiles for excited states of helium atom are also calculated. While the calculated CPs are found to generally agree, they differ slightly from one another for small values of the Compton parameter q and are in good agreement for large q values. The expectation values within the three theories are also found to be comparable. The HS formalism is seen to mimic HF reasonably well in the momentum space, establishing the logical consistency of the former. Received: 11 December 1998 / Received in final form: 20 April 1999     

Momentum densities and Compton profiles of alkali-metal atoms

It is assumed that the dynamics of valence electrons of alkali-metal atoms can be well accounted for by a quantum-defect theoretic model while the core electrons may be supposed to move in a self-consistent field. This model is used to study the momentum properties of atoms from³Li to³⁷Rb. The numerical results obtained for the momentum density, moments of momentum density and Compton profile are found to be in good agreement with the results of more detailed configuration-interaction calculations for the atom³Li. Similar results for¹¹Na,¹⁹K and³⁷Rb are compared with the corresponding Hartree-Fock-Roothaan values only, for want of data from other realistic calculations     

Compton profiles of metals and Van Hove singularities

The structures of the Compton profiles of metals, as observed by Platzman et al., are tentatively interpreted as Van Hove singularities for Bloch electrons.     

Compton profiles of liquid and solid lithium metals

Compton profile measurements have been performed on liquid and solid lithium metal using 59.54 keV γ-ray from ²⁴¹Am source. A difference between Compton profiles in both states has been found.     

Electron momentum distribution and Compton profiles of europium

The electron momentum distribution and Compton profiles of the rare earth element Eu was measured using HPGe photon detector. The target atoms were excited by means of 59.54 keV gamma rays from Am-241 radioactive source of strength 300 mCi. Elemental foil of uniform aerial density, and purity better than 99.9% was used as target. The data were recorded and analyzed using a 4 K multichannel analyzer. These data duly corrected for instrumental resolution effects, sample absorption, energy dependence of the differential Compton cross-section and double scattering, and compared with theoretical renormalized free atom (RFA) values.     

Local density functional approximation applied to Compton profiles

We have applied a self-consistent psuedopotential approach in the density functional approximation to study the dependence of the Compton profile of silicon on the choice of the exchange correlation potential. We find that the Compton profile depends strongly on the value of the exchange-correlation potential.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 76–79, January, 1996.     

APW-Xα Compton profiles in crystalline rare gases

Augmented Plane Wave, local exchange (APW-Xα) one-electron wave functions have been used to calculate Compton profiles for crystalline Ne at three different lattice constants for two values of the local exchange parameter. Some results for Ar, Kr, and Xe are also presented. The impulse approximation is used. The crystalline calculations are little different from the isolated atom results. A variety of difficulties, primarily due to the energy-dependent nature of the APW basis, are explored. A translational symmetry restriction that is particularly severe for APW calculations of Compton profiles is studied. In all, it is concluded that the APW scheme is ill-suited to the computation of the sort of non-energy quantity represented by a Compton profile.     

Electronic properties and Compton profiles of molybdenum dichalcogenides

We present the first ever experimental Compton profiles of molybdenum dichalcogenides (MoX₂; X=S and Te) using 20 Ci ¹³⁷Cs Compton spectrometer. To interpret our experimental data, we have computed the theoretical profiles, energy bands and density of states using linear combination of atomic orbitals method in the framework of density functional theory and its hybridisation with Hartree Fock. The energy bands and density of states using full potential linearised augmented plane wave method have also been computed. Both theories show the existence of the indirect band gap. In addition, the relative nature of bonding is explained in terms of equal-valence-electron-density profiles and valence band charge densities.