81 research outputs found
On the validity of power functionals for the homogeneous electron gas in reduced.density-matrix-functional theory
Physically valid and numerically efficient approximations for the exchange
and correlation energy are critical for reduced density-matrix functional
theory to become a widely used method in electronic structure calculations.
Here we examine the physical limits of power functionals of the form
for the scaling function in the exchange-correlation
energy. To this end we obtain numerically the minimizing momentum distributions
for the three- and two-dimensional homogeneous electron gas, respectively. In
particular, we examine the limiting values for the power to yield
physically sound solutions that satisfy the Lieb-Oxford lower bound for the
exchange-correlation energy and exclude pinned states with the condition
for all wave vectors . The results refine the
constraints previously obtained from trial momentum distributions. We also
compute the values for that yield the exact correlation energy and its
kinetic part for both the three- and two-dimensional electron gas. In both
systems, narrow regimes of validity and accuracy are found at and at for the density parameter, corresponding to
relatively low densities.Comment: Phys. Rev. A (in print, 2016
Superdeformation in Po
The Yb(Si,5n) reaction at 148 MeV with thin targets was used
to populate high-angular momentum states in Po. Resulting rays
were observed with Gammasphere. A weakly-populated superdeformed band of 10
-ray transitions was found and has been assigned to Po. This is
the first observation of a SD band in the region in a nucleus
with . The of the new band is very similar to those of
the yrast SD bands in Hg and Pb. The intensity profile suggests
that this band is populated through states close to where the SD band crosses
the yrast line and the angular momentum at which the fission process dominates.Comment: 10 pages, revtex, 2 figs. available on request, submitted to Phys.
Rev. C. (Rapid Communications
Intruder bands and configuration mixing in the lead isotopes
A three-configuration mixing calculation is performed in the context of the
interacting boson model with the aim to describe recently observed collective
bands built on low-lying states in neutron-deficient lead isotopes. The
configurations that are included correspond to the regular, spherical states as
well as two-particle two-hole and four-particle four-hole excitations across
the Z=82 shell gap.Comment: 20 pages, 4 figures, accepted by PRC, reference added for section 1
in this revised versio
Single step links of the superdeformed band in Pb-194:A measure of the absolute excitation energy, spin and parity of the superdeformed states
The EUROGAM array has been used to investigate the decay out of the yrast superdeformed (SD) band in Pb-194. Six single step decays from the lowest observed SD slates to low-lying states at normal deformation (ND) have been identified. From this observation, the excitation energy of the SD band in Pb-194 is established at 4877 +/- 1.5 keV for the 6(+) SD state. The most probable spins and parities of all members of the SD band are also deduced assuming that the SD states have even spin and positive parity
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