B12Hn and B12Fn: planar vs icosahedral structures

Using density functional theory and quantum Monte Carlo calculations, we show that B12Hn and B12Fn (n = 0 to 4) quasi-planar structures are energetically more favorable than the corresponding icosahedral clusters. Moreover, we show that the fully planar B12F6 cluster is more stable than the three-dimensional counterpart. These results open up the possibility of designing larger boron-based nanostructures starting from quasi-planar or fully planar building blocks

Review of Shape Phase Transition Studies for Bose-Fermi Systems: The Effect of the Odd-Particle on the Bosonic Core

The quantum phase transition studies we have done during the last few years for odd-even systems are reviewed. The focus is on the quantum shape phase transition in Bose-Fermi systems. They are studied within the Interacting Boson-Fermion Model (IBFM). The geometry is included in this model by using the intrinsic frame formalism based on the concept of coherent states. First, the critical point symmetries E(5/4) and E(5/12) are summarized. E(5/4) describes the case of a single j=3/2 particle coupled to a bosonic core that undergoes a transition from spherical to γ-unstable. E(5/12) is an extension of E(5/4) that describes the multi-j case (j=1/2,3/2,5/2) along the same transitional path. Both, E(5/4) and E(5/12), are formulated in a geometrical context using the Bohr Hamiltonian. Similar situations can be studied within the IBFM considering the transitional path from UBF(5) to OBF(6). Such studies are also presented. No critical points have been proposed for other paths in odd-even systems as, for instance, the transition from spherical to axially deformed shapes. However, the study of such shape phase transition can be done easily within the IBFM considering the path from UBF(5) (spherical) to SUBF(3) (axial deformed). Thus, in a second part, this study is presented for the multi-j case. Energy levels and potential energy surfaces obtained within the intrinsic frame formalism of the IBFM Hamiltonian are discussed. Finally, our recent works within the IBFM for a single-j fermion coupled to a bosonic core that performs different shape phase transitional paths are reviewed. All significant paths in the model space are studied: from spherical to γ-unstable shape, from spherical to axially deformed (prolate and oblate) shapes, and from prolate to oblate shape passing through the γ-unstable shape. The aim of these applications is to understand the effect of the coupled fermion on the core when moving along a given transitional path and how the coupled fermion modifies the bosonic core around the critical points

Investigation of A ? 100 mass region up to exotic with interacting boson model

CPAN-Ingenio 2010;University of Seville;University of Huelva;International University of Andalucia;Spanish Ministry of Science and Education2009 La Rabida International Scientific Meeting on Nuclear Physics: "Basic Concepts in Nuclear Physics: Theory, Experiments and Applications" -- 4 July 2009 through 10 July 2009 -- La Rabida --Even-even nuclei in the A ? 100 mass region are investigated within the framework of the interacting boson model-1 (IBM-1). The parametrization established on the basis of known elements is then used to predict properties of the unknown. This paper includes the predicted energy spectra and the potential energy surface obtained from the IBM-1 hamiltonian in the classical limit. © 2010 American Institute of Physics

Description of Exotic Nuclei with the Interacting Boson Model

International audienceEven—even nuclei in the A~100 mass region are investigated within the framework of the interacting boson model-1 (IBM-1). The study includes energy spectra and electric quadrupole transition properties of zirconium, molybdenum, ruthenium and palladium isotopes with neutron number N>=54. A global parametrization of the IBM-1 hamiltonian is found leading to a description of 301 collective levels in 30 nuclei with a root-mean-square deviation from the observed level energies of 119 keV. The geometric character of the nuclei can be visualized by plotting the potential energy surface V(beta,gamma) obtained from the IBM-1 hamiltonian in the classical limit. The parametrization established on the basis of known elements is then used to predict properties of the unknown, neutron-rich isotopes 106Zr, 112Mo, 116Ru and 120Pd

Unexpected transitional paths in the prolate to oblate shape phase transitions for Bose–Fermi systems

The quantum shape phase transitions in odd-even nuclei are investigated within the intrinsic frame approach to the interacting boson-fermion model. In this work, the case of a single-j fermion coupled to a bosonic core that performs a transition from prolate to oblate shapes is considered. The focus is on the effect of the coupled fermion on the whole system along the transitional path from prolate to oblate shapes, passing through the $${\gamma }$$-unstable shape. One could expect that all the magnetic substates of the coupled single-fermion with $$j=9/2$$ would be driven by the shape of the bosonic core. However, the present work shows that the odd-fermion follows some unexpected and unique paths. The five-components of the $$j=9/2$$ orbital do show quite interesting and diverse behaviour. Two of them move slowly from the prolate to the oblate shape by venturing into the triaxial region and also show $$\gamma$$-softness around their slow shape-changing region. The other three odd-states show sudden jumps from prolate side to oblate side and shape coexistence appears, although one of them is fairly close to $$\gamma$$-instability. These unexpected situations make this shape phase transition worth of investigation and discussion

Extended interacting boson model description of Pd nuclei in the A∼100 transitional region

Studies of even-even nuclei in the A∼100 transitional mass region within the framework of the interacting boson model-1 (IBM-1) have been expanded down to 98Pd nuclei to compare the calculation with new experimental results from measurements obtained at the Institute of Nuclear Physics in Cologne. The low-lying energy levels and the E2 transition rates of 98−100Pd nuclei are investigated and their geometric structures are described in the present work. We have also focused on the new B(E2:21+ → 01+) values of 112,114Pd nuclei to compare with previously calculated values