Magnetic and electronic properties of NiAs-type chromium chalcogenides

We have computed spin-dependent energy bands, spin moments and density of states of NiAs-type CrX (X=S, Se and Te) chalcogenides using linear combination of atomic orbitals method within density functional theory as well as full potential augmented plane wave method. In addition, magnetic properties have also been computed using spin polarized relativistic Korringa-Kohn-Rostoker method. We have also obtained the first ever theoretical electron momentum densities of CrX compounds considering linear combination of atomic orbitals and compared the results with the isotropic Compton profiles measured using 20 Ci ¹³⁷Cs Compton spectrometer. The Fermi surface topology and magnetic properties are discussed in terms of majority and minority energy bands and density of states. In addition, to highlight the role of Cr (3d) electrons in such type of chalcogenides, we have also reported the magnetic Compton profile of CrTe using the Korringa-Kohn-Rostoker method.     

Development of measuring magnetic Compton profiles by grazing incidence geometry

A novel technique of measuring a magnetic Compton profile using the grazing angle geometry against a sample surface (Grazing Incidence Magnetic Compton Profile) has been successively developed. Measurements of a magnetic moment and a magnetic Compton profile are possible for a Fe 200 nm film on a thick glass substrate. The estimated thinnest limit for measurements is 100 nm for a Fe film.     

Compton scattering and charge transfer in Er substituted DyAl2

A unique applicability of Compton spectroscopy in probing the electronic states of rare earth aluminides using high energy (662 keV) γ-rays is reported. We have measured first-ever Compton profiles of Dy_1-xEr_xAl₂ (x=0, 0.2) using 20Ci ¹³⁷Cs Compton spectrometer. The charge reorganization in Dy_1−xEr_xAl₂ (x=0, 0.2), on the formation of compound, has been discussed using the valence band Compton profile data. The experimental Compton profile data unambiguously establish charge transfer from Al to Dy (Dy and Er) on formation of x=0.0 (0.2) compound, which is in tune with spin polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) calculations. A reasonable agreement between SPR-KKR based Compton profiles and the experimental data show applicability of the Green function method in predicting the electronic properties of rare earth compounds.     

Observation of ionic deformation and bonding from compton profiles

We describe a new method of interpreting Compton profile data using a function B(r) which is the autocorrelation function of the one-electron wave function Ψ(r). In any particular direction B(r) can be obtained by a one-dimensional Fourier transform of the corresponding directional Compton profile. The technique is applied to LiF and it provides a means of determining the ionic radii, as well as locating some inadequacies in the tight-binding overlap model for ionic crystals.     

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.     

Electronic properties and compton profiles of silver iodide

We have carried out an extensive study of electronic properties of silver iodide in β- and γ-phases. The theoretical Compton profiles, energy bands, density of states and anisotropies in momentum densities are computed using density functional theories. We have also employed full-potential linearized augmented plane-wave method to derive the energy bands and the density of states. To compare our theoretical data, isotropic Compton profile measurement on γ-AgI using ¹³⁷Cs Compton spectrometer at an intermediate resolution of 0.38 a.u. has been undertaken. The theoretical anisotropies are also interpreted on the basis of energy bands.     

Self-consistent Compton profile of selenium

The valence electron Compton profile of trigonal and polycrystalline trigonal selenium has been determined using the self-consistent OPW method. The anisotropy of the Compton profile between directions parallel and perpendicular to the c-axis is discussed. The results are compared with experimental data. The difference of the Compton profiles of the amorphous and polycrystalline phases is examined.     

OPW calculation of the compton profile of beryllium

Compton profile of beryllium is calculated by OPW method using the potential constructed by Loucks and Cutler which had given good agreement with Fermi surface data. However, the computed profile compares poorly with the experiment.     

类氢离子的相对论康普顿轮廓（英文）

基于中心场近似得到Dirac径向轨道,并使用恰当的Fourier变换系统计算了类氢离子电子动量分布和康普顿轮廓。以H原子和Xe53+离子为例,探讨了相对论效应和原子核的有限体积效应对单电子康普顿轮廓的影响。同时,详细研究了单电子康普顿轮廓对主量子数n、轨道量子数l、单电子总角动量量子数j和核电荷数Z的依赖关系。结果表明,相对论效应可以扩展康普顿轮廓的分布,并且使给定nl的轨道随着Z的增加分裂得越来越明显。然而,相对论效应也会随着主量子数n和轨道量子数l的增加而减弱。同时,对于nl_j轨道,其康普顿轮廓还具有n-l个平台的结构。另外,原子核的有限体积几乎不会影响H原子和Xe53+离子的康普顿轮廓。The Compton profiles of the electron in the ground and excited states of H-like ions have been calculated systematically with one-electron Dirac radial orbitals by using the proper Fourier transformation. Taking the H atom and Xe53+ ion as examples, the effects of relativity and finite nuclear size on Compton profile have been discussed. Furthermore, the dependence of one-electron Compton profile on the principle quantum number n, orbital quantum number l, angular quantum number j and nuclear charge Z has also been discussed. It is found that the relativistic effect can expand the distribution of the Compton profile and split the orbital more and more obviously for given nl(l=0) as increasing Z. However, the relativistic effect can gradually weaken with the increase of the principal quantum number n and orbital quantum number l. Furthermore, the Compton profile of the orbital with quantum number nl_j has certain number of platforms that is n-l. In addition, the nuclear finite size hardly affects the Compton profile for H atom and Xe53+ ion.     

Electron momentum density, band structure, and structural properties of SrS

The electron momentum density, the electronic band structure, and the structural properties of SrS are presented in this paper. The isotropic Compton profile, anisotropies in the directional Compton profiles, the electronic band structure and density of states are calculated using the ab initio periodic linear combination of atomic orbitals method with the CRYSTAL06 code. Structural parameters of SrS—lattice constants and bulk moduli in the B1 and B2 phases—are computed together with the transition pressure. The computed parameters are well in agreement with earlier investigations. To compare the calculated isotropic Compton profile, measurement on polycrystalline SrS is performed using 5Ci-²⁴¹Am Compton spectrometer. Additionally, charge transfer is studied by means of the Compton profiles computed from the ionic model. The nature of bonding in the isovalent SrS and SrO compounds is compared on the basis of equal-valenceelectron-density profiles and the bonding in SrS is found to be more covalent than in SrO.     

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.     

Determination of Fermi momentum using Fourier transformed Compton profile

We examine the effect of electron correlations on the Fourier transformed Compton profile (FTCP) and on the use of FTCP for determining the Fermi momentum.     

浅析影响康普顿谱线位置的因素

康普顿散射中影响康普顿谱线位置的因素是十分复杂的,文章主要针对影响康普顿谱线位置的几个因素作了理论探讨,得出影响因素主要在于:电子具有初速度会增大散射波长的改变量;束缚能的存在要减小峰值波长的改变量;双光子散射和二次散射与谱线峰值位置的关系不大,二者对峰值波长的改变是不确定的、复杂的、在连续的范围内变化的.最后对康普顿谱线位置和康普顿轮廓的理论研究和应用前景作了展望.     

Magnetic Compton scattering study of NpNiGa5

We have carried out the magnetic Compton scattering of NpNiGa₅. The signs of the magnetic effects in both ordered states are negative. These facts demonstrate that the contribution of the Np 5f electrons is dominant in the ordered states of NpNiGa₅. The magnetic Compton profile shows significant change across the successive transitions. This suggests that the successive transitions are correlated with the 5f quadrupolar degrees of freedom and/or the change of the quantized axis.     

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.     

Band structure,optical properties,and compton profile of copper

A self-consistent calculation of the band structure of copper has been performed using a basis of gaussian orbitals and a local exchange-correlation potential. Results are also presented for the optical conductivity and the Compton profile.     

Self-consistent LCAO local density determination of anisotropic compton profile and X-ray structure factors in diamond

Our newly developed fully Self-Consistent Numerical Discrete Variational Method (which exactly treats all non-spherical parts of the crystal potential) yields X-ray scattering factors and anisotropies in the Compton profile of diamond in very good agreement with experiment.     

GW approximation study of the Compton profile of ZnSe

We have obtained the Compton profile of ZnSe from the first principles GW approximation (GWA) method and ground-state density functional theory (DFT) method. We observe that between 0 and 1.5?a.u., there is better agreement to previous studies via the GWA difference profile compared to the ground-state difference profile. Above 1.5?a.u., both cases do not agree with the trend of the previous study; however, the application of the GWA is seen to improve the agreement compared to localized density approximation. Previous studies have reported that discrepancies from experiment are related to pseudopotential calculations which have been observed to overestimate momentum density between 0 and 1.5?a.u., while the reverse trend is seen above 1.5?a.u. We thus conclude that improvement to the pseudopotential technique to obtain the Compton profile is possible if the sharp Fermi break of the momentum distribution between high and low momenta becomes more smeared. Using the broadened spectral functions via the contour deformation method to obtain the momentum distributions, the GWA is a natural tool to achieve this via the contribution from the dielectric screening to the quasiparticle energies.     

Compton scattering study and electronic properties of vanadium carbide: A validation of hybrid functional

In this paper, we have reported the isotropic Compton profile of VC measured using high energy (661.65 keV) γ-radiations from a ¹³⁷Cs isotope. To compare the experimental momentum densities, we have also employed the linear combination of atomic orbitals (LCAO). In addition, energy bands, density of states and Fermi surface topology of VC have been computed using FP-LAPW and LCAO methods. It is seen that the LCAO with hybridization of density functional theory and Hartree-Fock (so called B3LYP) gives a better agreement with the present Compton profile experiment. This shows validation of an exact exchange part in hybrid density functional. On the basis of energy bands, we have discussed the microscopic origin for the anomalous behavior of hardness of VC. The relative nature of bonding in VC and NbC is also discussed in terms of valence charge densities and Mulliken′s population analysis. To establish the role of Compton profiles in computation of cohesive properties of refractory materials, we have also calculated for the first time the cohesive energy using the present experimental Compton profile and compared it with the existing data.     

On the bremsstrahlung background correction to the high-energy Compton spectroscopy

methodology for bremsstrahlung (BS) background correction to extract a true Compton profile in high-energy Compton scattering experiments is presented. The BS background profiles for Hg, computed within the Born approximation, are estimated for different values of incident energy. It is seen for the first time that the BS background contribution in high-energy Compton profile experiments like those employing third generation synchrotron radiation sources comes out to be significant and non-linear. Further, it is found that the incorporation of BS correction in data reduction of such an experiment performed on Hg at 662 keV energy helps in reconciliation of theory and experiment.