13,119 research outputs found
Microscopic description of fission in neutron-rich plutonium isotopes with the Gogny-D1M energy density functional
The most recent parametrization D1M of the Gogny energy density functional is
used to describe fission in the isotopes Pu. We resort to the
methodology introduced in our previous studies [Phys. Rev. C \textbf{88},
054325 (2013) and Phys. Rev. C \textbf {89}, 054310 (2014)] to compute the
fission paths, collective masses and zero point quantum corrections within the
Hartree-Fock-Bogoliubov framework. The systematics of the spontaneous fission
half-lives t, masses and charges of the fragments in Plutonium isotopes
is analyzed and compared with available experimental data. We also pay
attention to isomeric states, the deformation properties of the fragments as
well as to the competition between the spontaneous fission and -decay
modes. The impact of pairing correlations on the predicted t values is
demonstrated with the help of calculations for Pu in which the
pairing strengths of the Gogny-D1M energy density functional are modified by 5
and 10 , respectively. We further validate the use of the D1M
parametrization through the discussion of the half-lives in Fm. Our
calculations corroborate that, though the uncertainties in the absolute values
of physical observables are large, the Gogny-D1M Hartree-Fock-Bogoliubov
framework still reproduces the trends with mass and/or neutron numbers and
therefore represents a reasonable starting point to describe fission in heavy
nuclear systems from a microscopic point of view.Comment: 14 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1312.722
Microscopic description of fission in nobelium isotopes with the Gogny-D1M energy density functional
Constrained mean-field calculations, based on the Gogny-D1M energy density
functional, have been carried out to describe fission in the isotopes
No. The even-even isotopes have been considered within the standard
Hartree-Fock-Bogoliobov (HFB) framework while for the odd-mass ones the Equal
Filling Approximation (HFB-EFA) has been employed. Ground state quantum numbers
and deformations, pairing energies, one-neutron separation energies, inner and
outer barrier heights as well as fission isomer excitation energies are given.
Fission paths, collective masses and zero-point quantum vibrational and
rotational corrections are used to compute the systematic of the spontaneous
fission half-lives t both for even-even and odd-mass nuclei.
Though there exists a strong variance of the predicted fission rates with
respect to the details involved in their computation, it is shown that both the
specialization energy and the pairing quenching effects, taken into account
within the self-consistent HFB-EFA blocking procedure, lead to larger
t values in odd-mass nuclei as compared with their even-even
neighbors. Alpha decay lifetimes have also been computed using a
parametrization of the Viola-Seaborg formula. The high quality of the Gogny-D1M
functional regarding nuclear masses leads to a very good reproduction of
values and consequently of lifetimes.Comment: 13 pages, 9 figure
Microscopic description of fission in Uranium isotopes with the Gogny energy density functional
The most recent parametrizations D1S, D1N and D1M of the Gogny energy density
functional are used to describe fission in the isotopes U. Fission
paths, collective masses and zero point quantum corrections, obtained within
the constrained Hartree-Fock-Bogoliubov approximation, are used to compute the
systematics of the spontaneous fission half-lives , the masses
and charges of the fission fragments as well as their intrinsic shapes. The
Gogny-D1M parametrization has been benchmarked against available experimental
data on inner and second barrier heights, excitation energies of the fission
isomers and half-lives in a selected set of Pu, Cm, Cf, Fm, No, Rf, Sg, Hs and
Fl nuclei. It is concluded that D1M represents a reasonable starting point to
describe fission in heavy and superheavy nuclei. Special attention is also paid
to understand the uncertainties in the predicted values arising
from the different building blocks entering the standard semi-classical
Wentzel-Kramers-Brillouin formula. Although the uncertainties are large, the
trend with mass or neutron numbers are well reproduced and therefore the theory
still has predictive power. In this respect, it is also shown that
modifications of a few per cent in the pairing strength can have a significant
impact on the collective masses leading to uncertainties in the
values of several orders of magnitude.Comment: 22 pages, 17 figures; Minor modifications to previous versio
Role of Strain on Electronic and Mechanical Response of Semiconducting Transition-Metal Dichalcogenide Monolayers: an ab-initio study
We characterize the electronic structure and elasticity of monolayer
transition-metal dichalcogenides MX2 (M=Mo, W, Sn, Hf and X=S, Se, Te) with 2H
and 1T structures using fully relativistic first principles calculations based
on density functional theory. We focus on the role of strain on the band
structure and band alignment across the series 2D materials. We find that
strain has a significant effect on the band gap; a biaxial strain of 1%
decreases the band gap in the 2H structures, by as a much 0.2 eV in MoS2 and
WS2, while increasing it for the 1T materials. These results indicate that
strain is a powerful avenue to modulate their properties; for example, strain
enables the formation of, otherwise impossible, broken gap heterostructures
within the 2H class. These calculations provide insight and quantitative
information for the rational development of heterostructures based on these
class of materials accounting for the effect of strain.Comment: 16 pages, 4 figures, 1 table, supplementary materia
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