32,214 research outputs found
On the use of the approximation in atomic calculations
We demonstrate that approximation is a good starting point for the
configuration interaction calculations for many-electron atoms and ions. is
the total number of electrons in the neutral atom, is the number of valence
electrons. is the self-consistent Hartree Fock potential for a
closed-shell ion with all valence electrons removed. Using of the
approximation considerably simplifies the many-body perturbation theory for the
core-valence correlations. It makes it easier to include higher-order
correlations which often significantly improves the accuracy of the
calculations. Calculations for krypton and barium and their positive ions are
presented for illustration.Comment: 5 pages,1 figure, submitted to Phys. Rev.
A planned program for developing word perception in grade one
Thesis (Ed.M.)--Boston Universit
Sparticle Production in Electron-Photon Collisions
We explore the potential of electron-photon colliders to measure fundamental
supersymmetry parameters via the processes
(selectron-neutralino) and
(sneutrino-chargino). Given the and masses from
and hadron collider studies, cross section ratios
for opposite photon helicities determine
the , and masses, independent of the
sparticle branching fractions. The difference measures in a model-independent way. The
and masses test the universality of soft supersymmetry breaking
scalar masses. The cross section normalizations provide information about the
gaugino mixing parameters.Comment: add refs; add \tightenline
Retention and application of Skylab experiences to future programs
The problems encountered and special techniques and procedures developed on the Skylab program are described along with the experiences and practical benefits obtained for dissemination and use on future programs. Three major topics are discussed: electrical problems, mechanical problems, and special techniques. Special techniques and procedures are identified that were either developed or refined during the Skylab program. These techniques and procedures came from all manufacturing and test phases of the Skylab program and include both flight and GSE items from component level to sophisticated spaceflight systems
Band gaps in pseudopotential self-consistent GW calculations
For materials which are incorrectly predicted by density functional theory to
be metallic, an iterative procedure must be adopted in order to perform GW
calculations. In this paper we test two iterative schemes based on the
quasi-particle and pseudopotential approximations for a number of inorganic
semiconductors whose electronic structures are well known from experiment.
Iterating just the quasi-particle energies yields a systematic, but modest
overestimate of the band gaps, confirming conclusions drawn earlier for CaB_6
and YH_3. Iterating the quasi-particle wave functions as well gives rise to an
imbalance between the Hartree and Fock potentials and results in bandgaps in
far poorer agreement with experiment.Comment: 5 pages, 2 figures, 2 table
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