2,050 research outputs found
Implications of non-feasible transformations among icosahedral orbitals
The symmetric group that permutes the six five-fold axes of an
icosahedron is introduced to go beyond the simple rotations that constitute the
icosahedral group . Owing to the correspondence , the
calculation of the Coulomb energies for the icosahedral configurations
based on the sequence can be brought
to bear on Racah's classic theory for the atomic d shell based on . Among the elements of is the kaleidoscope
operator that rotates the weight space of SO(5) by . Its use
explains some puzzling degeneracies in d^3 involving the spectroscopic terms
^2P, ^2F, ^2G and ^2H.Comment: Tentatively scheduled to appear in Physical Preview Letters Apr 5,
99. Revtex, 1 ps figur
Multipole decomposition of LDA+ energy and its application to actinides compounds
A general reformulation of the exchange energy of -shell is applied in
the analysis of the magnetic structure of various actinides compounds in the
framework of LDA+U method. The calculations are performed in an efficient
scheme with essentially only one free parameter, the screening length. The
results are analysed in terms of different polarisation channels, due to
different multipoles. Generally it is found that the spin-orbital polarisation
is dominating. This can be viewed as a strong enhancement of the spin-orbit
coupling in these systems. This leads to a drastic decrease in spin
polarisation, in accordance with experiments. The calculations are able to
correctly differentiate magnetic and non-magnetic Pu system. Finally, in all
magnetic systems a new multipolar order is observed, whose polarisation energy
is often larger in magnitude than that of spin polarisation.Comment: Fixed some references and picture
Alternative Mathematical Technique to Determine LS Spectral Terms
We presented an alternative computational method for determining the
permitted LS spectral terms arising from electronic configurations. This
method makes the direct calculation of LS terms possible. Using only basic
algebra, we derived our theory from LS-coupling scheme and Pauli exclusion
principle. As an application, we have performed the most complete set of
calculations to date of the spectral terms arising from electronic
configurations, and the representative results were shown. As another
application on deducing LS-coupling rules, for two equivalent electrons, we
deduced the famous Even Rule; for three equivalent electrons, we derived a new
simple rule.Comment: Submitted to Phys. Rev.
An efficient approach for spin-angular integrations in atomic structure calculations
A general method is described for finding algebraic expressions for matrix
elements of any one- and two-particle operator for an arbitrary number of
subshells in an atomic configuration, requiring neither coefficients of
fractional parentage nor unit tensors. It is based on the combination of second
quantization in the coupled tensorial form, angular momentum theory in three
spaces (orbital, spin and quasispin), and a generalized graphical technique.
The latter allows us to calculate graphically the irreducible tensorial
products of the second quantization operators and their commutators, and to
formulate additional rules for operations with diagrams. The additional rules
allow us to find graphically the normal form of the complicated tensorial
products of the operators. All matrix elements (diagonal and non-diagonal with
respect to configurations) differ only by the values of the projections of the
quasispin momenta of separate shells and are expressed in terms of completely
reduced matrix elements (in all three spaces) of the second quantization
operators. As a result, it allows us to use standard quantities uniformly for
both diagona and off-diagonal matrix elements
Two-Center Integrals for r_{ij}^{n} Polynomial Correlated Wave Functions
All integrals needed to evaluate the correlated wave functions with
polynomial terms of inter-electronic distance are included. For this form of
the wave function, the integrals needed can be expressed as a product of
integrals involving at most four electrons
Characterization of anomalous Zeeman patterns in complex atomic spectra
The modeling of complex atomic spectra is a difficult task, due to the huge
number of levels and lines involved. In the presence of a magnetic field, the
computation becomes even more difficult. The anomalous Zeeman pattern is a
superposition of many absorption or emission profiles with different Zeeman
relative strengths, shifts, widths, asymmetries and sharpnesses. We propose a
statistical approach to study the effect of a magnetic field on the broadening
of spectral lines and transition arrays in atomic spectra. In this model, the
sigma and pi profiles are described using the moments of the Zeeman components,
which depend on quantum numbers and Land\'{e} factors. A graphical calculation
of these moments, together with a statistical modeling of Zeeman profiles as
expansions in terms of Hermite polynomials are presented. It is shown that the
procedure is more efficient, in terms of convergence and validity range, than
the Taylor-series expansion in powers of the magnetic field which was suggested
in the past. Finally, a simple approximate method to estimate the contribution
of a magnetic field to the width of transition arrays is proposed. It relies on
our recently published recursive technique for the numbering of LS-terms of an
arbitrary configuration.Comment: submitted to Physical Review
Multipolar Interactions in the Anderson Lattice with Orbital Degeneracy
Microscopic investigation is performed for intersite multipolar interactions
in the orbitally degenerate Anderson lattice, with CeB taken as an
exemplary target. In addition to the intermediate state,
Hund's-rule ground states are included as intermediate states for the
interactions. The conduction-band states are taken as plane waves and the
hybridization as spherically symmetric. The spatial dependences of multipolar
interactions are given by the relative weight of partial wave components along
the pair of sites. It is clarified how the the anisotropy arises in the
interactions depending on the orbital degeneracy and the spatial configuration.
The stability of the antiferro-quadrupole order in the phase II of
CeB is consistent with our model. Moreover, the pseudo-dipole interactions
follow a tendency required by the phenomenological model for the phase III.Comment: 30 pages, 4 figure
Improved Procedures for Purification of the Bandeiraea simplicifolia I Isolectins and Bandeiraea simplicifolia II Lectin by Affinity Chromatography
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66350/1/j.1432-1033.1980.tb07197.x.pd
Structural analysis of the Ss sialoglycoprotein specific for Henshaw blood group from human erythrocyte membranes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66122/1/j.1432-1033.1984.tb08155.x.pd
Coordinated Tax-Tariff Reforms, Informality, and Welfare Distribution
The paper studies the revenue, efficiency, and distributional implications of a simple strategy of offsetting tariff reductions with increases in destination-based consumption taxes so as to leave consumer prices unchanged. We employ a dynamic micro-founded macroeconomic model of a small open developing economy, which features an informal sector that cannot be taxed, a formal agricultural sector, and an import-substitution sector. The reform strategy increases government revenue, imports, exports, and the informal sector. In contrast to Emran and Stiglitz (2005), who ignore the dynamic effects of taxes and tariffs on factor markets, we find an efficiency gain, which is unevenly distributed. Existing generations benefit more than future generations, who (depending on pre-existing tax and tariff rates and the informal sector size) even may become worse off
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