A single parameter scaling theory in a disordered layered system

We show that in a disordered layered system all states are localized if k_Fl<4Πg_c, irrespective of the interlayer coupling t _⊥. The crossover of dimensionality depends on t_⊥. Near the critical value t_⊥^c at which the Anderson transition occurs, the correlation length ζ^m and the localization length ζ^loc are calculated.     

Energy Levels and Spectroscopic Parameters of Neodymium Trifluorides

A great deal of spectroscopic work has been done in the last decade to study rare earths in different environments. Recently, crystals of NdF₃ and NdF₃ doped with hydrogen and deuterium have been studied¹ spectroscopically and, from the extra electronic lines appearing on the longer wave lenght side of the usual rare earth electronic transititions, the isotope shift have been calculated. Since no informations, regarding interelectronic repulsion, spin-orbit interaction, nephelauxetic effect, bonding, electronic energy states and nature of transitions involved, have yet been obtained, it was thought worthwile to carry out the present calculations.

The present communication reports the values of Slater-Condon (F_k), Racah (E^k), and Lande (4f) parameters for HdF₃, Hyd. NdF₃ and Deu. HdF₃ crystals.     

Dirac-Fock studies of some electronic properties of actinide ions

Results of accurate Dirac-Fock studies of some U, Np, Pu and Am ions are reported; these include one-electron eigen-values, spin-orbit splittings, 〈rⁿ〉 values for the 5f electrons, Slater F^k and G^k integrals, Mössbauer isomer shift electronic densities and the 〈j_i〉 integrals needed for neutron magnetic form factors.     

Neutron Matter Properties Using Skyrme Interaction

The purpose of the present work is to extend earlier nuclear matter calculations to study the properties of neutron matter. The binding energy per particle, symmetry energy, single particle potential, effective mass, and magnetic susceptibility are calculated using a modified Skyrme interaction. These are calculated as a function of the Fermi momentum k_f in the range 0 < k_f < 2 fm^?1. Two sets of the interaction parameters are obtained by fitting the interaction parameters using the available information on neutron matter. Relativistic corrections to the order 1/c² are also calculated. The relativistic corrections are very small and they increase as k_f is increased.     

Calculation of Landau's fermi-liquid parameters in pure neutron matter

The Landau parameters F₀, F₁, G₀ and G₁ have been calculated in pure neutron matter including the interaction induced by exchange of density-density and spin-density excitations at densities up to k_F = 2.5 fm^?1. The main effect of the induced interaction is to make the matter more incompressible.     

Optical absorption spectrum of Ni2+ ion doped in synthetic lecontite

The optical absorption spectrum of Ni²⁺ ion doped in lecontite (sodium ammonium sulphate dihydrate) single crystal has been studied at room and liquid air temperatures. All the bands could be assigned assumingO _h symmetry for the Ni²⁺ ion in the crystal. The splitting of³ T _1g (F) band at liquid air temperature has been attributed to spin-orbit interaction. The crystal field and spin-orbit parameters derived areD _q=1000 cm^?1;B=740 cm^?1;C/B=4.27 and ζ=600 cm^?1. All the bands observed show a blue shift when the crystal was cooled to liquid air temperature.     

Use of sturmian expansions in calculations of the hyperfine structure of atomic spectra

A procedure for calculating hyperfine structure (HFS) parameters using the basis of Sturmian functions is developed. The procedure is used to calculate the HFS parameter a _4d ⁵ of the 4d ⁵ levels of the niobium atom. The contributions of the continuous spectrum and higher orders of the perturbation theory are quantitatively estimated by comparing the numerical values of the parameter a _4d ¹⁰ obtained in the framework of the perturbation theory with the results of direct calculations by the configuration interaction method. Comparison of the results of relativistic and nonrelativistic calculations allows the contribution of relativistic effects to HFS parameters to be found.     

Per cent ‘covalency’ and the nephelauxetic effect in lanthanide complexes

The use of the nephelauxetic ratio for the calculation of percent covalency is examined. Values of F_k and E^k obtained from four parameter fits (e.g. F ₂, F ₄, F ₆ and ζ_4f) neglecting configuration interaction for Pr³⁺ in various host lattices are compared to those of the free ion. By including the effects of 4f-ligand overlap one can account for the empirically obtained order of sensitivity to the environment for F_k : F ₂ > F ₄ > F ₆ and for E^k : E ² > E ³ > E ¹. The results further indicate that by using the nephelauxetic effect and the relationship b = (1 - β)/2 one is likely to overestimate the degree of covalency of a complex.     

Simulation of the fben d transitions of lanthanide ions in YPO4 using quantum-chemical calculations

We constructed an effective one-electron Hamiltonian by using the 4f/5d energies and eigenvectors obtained from the first-principles calculation with the relativistic self-consistent discrete variational Slater software package (DV-Xα). From the effective Hamiltonian, we obtained the crystal-field and spin-orbit interaction parameters for the 4f and 5d electrons of lanthanide ions (Ce³⁺, Pr³⁺, Nd³⁺ and Eu³⁺⁾ doped in YPO₄, and these parameters were used to calculate the 4f^N-4f^N-15d transition. Comparison with experiments shows that the obtained parameters are reasonable and the excitation spectra can be well predicted.     

Relativistic corrections and very small g-shifts in solids

The relativistic Breit-Margenau correction to the Zeeman-interaction has been calculated for a group of atoms in the periodic table with Herman Skillman wave functions and potentials. The results are applied to the S-state ions Mn²⁺ and Gd³⁺, to the F-center and V_k-center, and to the shallow donors in Si.     

Energy level scheme and the effect of magnetic order on the optical transitions in europium chalcogenides

The optical constants of Eu-chalcogenide single crystals have been determined at room temperature for photon energies from 1 to 6 eV. In the same energy range the transmission of thin evaporated films (except for EuO) has been measured with polarized light above and below the magnetic ordering temperature. The observed polarization-dependent splittings of the two main absorption maxima in the region of magnetic order suggest transitions from the 4f⁷-level into the crystal field split 5dt_2g- and 5de_g-states. An attempt has been made to relate the maxima of the absorption coefficient to interband transitions and transitions from the localized 4f-states. With this assumption we derived a consistent energy level scheme of the four Eu-chalcogenides. From the scheme we gained useful information about the width of the 5d-states, the crystal field splitting and the possible type of conductivity. Finally we tried to explain theoretically the splittings observed in the region of magnetic order. For this purpose a one-particle model has been used to calculate the transition probabilities for the 4f⁷?4f⁶(⁷F _J ) 5dt_2g and the 4f⁷?4f⁶(⁷F _J ) 5de_g transition, taking into account an exchange interaction as well as a spin-orbit coupling. Although this simple model can explain the splittings of the excited 4f⁶(⁷F _J ) 5de_g-state, a complete explanation of the effect of magnetic order on the 4f⁶(⁷F _J ) 5dt_2g-state fails up to now.     

Electronic structure and magnetism of CeCoGe3

The electronic band structure of CeCoGe₃ has been calculated using the self-consistent full potential nonorthogonal local orbital minimum basis scheme based on density functional theory. We investigated the electronic structure with the spin-orbit interaction and on-site Coulomb potential for the Ce-derived 4f orbitals to obtain the correct ground state of CeCoGe₃. The exchange interaction between local f electrons and conduction electrons play an important role in their heavy fermion characters. The fully relativistic band structure scheme shows that spin-orbit coupling splits the 4f states into two manifolds, the 4f_7/2 and the 4f_5/2 multiplets.     

Electronic structure and magnetism of YbRhSn

The electronic band structure of YbRhSn has been calculated using the self-consistent full potential nonorthogonal local orbital minimum basis scheme based on the density functional theory. We investigated the electronic structure with the spin-orbit interaction and on-site Coulomb potential for the Yb-derived 4f orbitals to obtain the correct ground state of YbRhSn. The exchange interaction between local f electrons and conduction electrons play an important role in the heavy fermion characters of them. The fully relativistic band structure scheme shows that spin-orbit coupling splits the 4f states into two manifolds, the 4f_7/2 and the 4f_5/2 multiplet.     

Comparative ab initio studies of small tin and lead clusters

We have performed ab initio total-energy pseudopotential calculations on neutral and negatively charged Snn and Pb_n (n = 3 ? 10) clusters. The lowest energy structures have been determined for all clusters, and the stabilities of neutral clusters were investigated by comparing their evaporation energies and stability functions. Clusters with n = 7,10 were found to be most stable while the clusters with n = 8 and Pb_s were much less stable, in agreement with features of the observed mass spectra. Calculations on Sn^?_n and Pb^?_n show that both atomic and electronic structures of a neutral cluster change substantially upon charging. The densities of states of Sn^?_n clusters reproduce the main features of the experimental photoelectron spectra. The agreement is poorer for Pb^?_n clusters where the calculations underestimate the separation between energy levels which we think is due to the larger spin-orbit splitting in Pb, which was neglected in the calculations. We found that the differences between Sn and Pb clusters cannot be completely addressed without a more complete accounting of relativistic effects. The electron affinities of Sn_n and Pb_n clusters have also been calculated and the results agree fairly well with experimental values. Finally we considered Sn^2?₄ and Pb^2?₄ clusters and related the results to the formation of Zintl anions in liquid alkali-Sn and alkali-Pb alloys.     

Spin dynamics of the intermediate-valence compound EuCu<Subscript>2</Subscript>Si<Subscript>2</Subscript>

The dynamic magnetic response of the intermediate-valence compound EuCu₂Si₂ has been studied using inelastic neutron scattering. At low temperatures, strong renormalization of the ⁷ F ₀ → ⁷ F ₁ spin-orbit transition energy is detected; it is likely to be related to partial delocalization of the f electrons of Eu. An increase in the temperature increases the valence instability of europium and results in further changes in the magnetic excitation spectrum parameters and the appearance of an intense quasi-elastic component.     

Energy levels calculation for Er3+: LiYF4

The complete configuration 4f¹¹ of Er³⁺ was diagonalized with a Hamiltonian containing electrostatic, two-body and three-body configuration interaction, spin-orbit and crystal field parameters of LiYP₄. A set of 18 parameters was adjusted to fit the experimental energy levels as given by Petrov and Tkachuk.     

A luminescence study of B-type Eu2O3 under pressure

Abstract

Luminescence spectra from Eu³ + ion in B-type (monoclinic) ₂O₃ powder have been recorded at room temperature as a function of pressure using a diamond anvil cell. Changes in the spectral pattern of the Eu³ + ion emission at about 4 GPa indicated that a phase transition to the A-type (hexagonal) structure had taken place. Upon release of the applied pressure, the B-type structure was regained with hysteresis. The spectral shifts with pressure have been used to study the effect of pressure on the spin-orbit interaction of the 4f electrons in the Ed + ion. The relationship between the relative changes in the spin-orbit coupling constant, ζ_4f, and the volume accompanying the phase transition is also discussed.     

Hyperfine Interactions in Pb<Superscript>3+</Superscript>F<Stack><Subscript>8</Subscript><Superscript>−</Superscript></Stack>F<Stack><Subscript>a</Subscript><Superscript>−</Superscript></Stack> clusters in fluorite crystals

The parameters of hyperfine interactions in Pb³⁺F ₈ ^? F _a ^? tetragonal clusters of MeF₂ crystals (Me=Ca, Sr, Ba) are interpreted. The contributions of the spin polarization to the parameters of the proper hyperfine interaction and additional (ligand) hyperfine interactions are calculated in the approximation of weak binding between a charge-compensating ion F _a ^? and a cubic fragment in the tetragonal cluster. It is demonstrated that correct inclusion of the contributions from the spin polarization to the ligand isotropic hyperfine interaction for the F _a ^? ion leads to anomalously large parameters of this interaction for MeF₂ crystals. These results are in agreement with experimental data.