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[en] Highlights: • A new direct scheme for quantum dynamics simulations of photoexcited states. • Automatic generation of potential energy surfaces with machine learning. • Propagation of diabatic states enables direct grid-based quantum dynamics. • Requires fewer electronic structure evaluations than generation of fitted diabatic surfaces. We present a method for performing non-adiabatic, grid-based nuclear quantum dynamics calculations using diabatic potential energy surfaces (PESs) generated “on-the-fly”. Gaussian process regression is used to interpolate PESs by using electronic structure energies, calculated at points in configuration space determined by the nuclear dynamics, and diabatising the results using the propagation diabatisation method reported recently (Richings and Worth, 2015). Our new method is successfully demonstrated using a grid-based approach to model the non-adiabatic dynamics of the butatriene cation. Overall, our scheme offers a route towards accurate quantum dynamics on diabatic PESs learnt on-the-fly.
[en] We have studied the fission parameters of hot neutron-rich thermally fissile and nuclei within the temperature dependent effective field theory motivated relativistic mean field (E-TRMF) formalism by using the recently developed FSUGarnet and IOPB-I parameter sets. The results obtained by these two forces are compared with the results of the well known and widely accepted NL3 parameter set. The excitation energy , shell correction energy , single particle energy for neutrons and protons , level density parameter a, neutron skin thickness ΔR, two neutron separation energy , and asymmetry energy coefficient of these neutron-rich thermally fissile nuclei are calculated at finite temperature. The dependency of level density parameter and other observables on the temperature and the force parameters (interaction Lagrangian) are discussed.
[en] The first (namely, inner) fission barriers for even-A N = 152 nuclei have been studied systematically in the framework of macroscopic-microscopic model by means of potential energy surface (PES) calculations in the three-dimensional () deformation space. Their collective properties, such as ground-state deformations, are compared with previous calculations and available observations, showing a consistent trend. In addition, it has been found that the microscopic shell correction energy plays an important role on surviving fission in these N = 152 deformed shell nuclei. The inclusion of non-axial symmetric degree of freedom γ will pull the fission barrier down more significantly with respect to the calculation involving in hexadecapole deformation β 4. Furthermore, the calculated Woods-Saxon (WS) single particle levels indicate that the large microscopic shell correction energies due to low level densities may be responsible for such a reduction on the inner fission barrier. (paper)
[en] New calculations of fission barrier heights in a five-dimensional (5D) deformation space for actinide nuclei have been performed based on a macro-microscopic (MM) model. To calculate potential energy surface (PES), we use the 5D generalized Lawrence shape (GLS) realistic parameterization as the shape description, the Lublin-Strasbourg Drop (LSD) model for the macroscopic energy and the folded-Yukawa model as the single-particle potential. A method to use two-center oscillator basis in calculating Hamiltonian matrix on any kind of shape description was presented. For the pairing energy, we use the SBCS model. Finally, Strutinsky method is used to calculate the microscopic correction energy. To find the fission barriers and fission paths, some concepts, such as basins, edges and neighbors from geography, are extended to identify the topographical structures on the 5D PES and we assume that the fission path follows the line of steepest descent. The fission barriers and double-humped paths of U and Pu isotopes are calculated.
[en] The problem of finding the highest limiting Z in the extended periodic table is discussed. The upper limit suggested by the atomic many body theory at Z = 172 may be reached much earlier due to nuclear instabilities. Therefore, an extensive set of calculations based on the relativistic mean field formulation are carried out for the ground state properties of nuclei with Z = 100 to 180 and N/Z ratio ranging from 1.19 to 2.70. This choice of Z and N extends far beyond the corresponding values of all the known heavy to superheavy elements. To facilitate the analysis of the huge quantity of calculated results, various filters depending upon the pairing energies, one and two nucleon separation energies, binding energy per particle (BE/A) and α-decay plus fission half lives, are introduced. The limiting value of Z is found to be 146. For the specific filter with 5.5 MeV a few nuclei with Z = 180 also appear. No evidence for the limiting Z value 172 is found. We stress the need to bridge the atomic and nuclear findings and to arrive at an acceptable limiting value of highest Z (or rather combination of Z and N) of the extended periodic table. (paper)
[en] Based on kinetic theory of ideal gas, the present work gives an indirect measurement on relativistic temperature transformation by using transverse momentum distribution of particles. Our result shows that Planck–Einstein relation is right. A moving system which has no energy current exchange with external surroundings becomes cool. (author)
[en] Encouraged by the evidence for Z = 6 magic number in neutron-rich carbon isotopes, we have performed relativistic mean-field plus BCS calculations to investigate ground state properties of entire chains of isotopes (isotones) with Z (N) = 6 including even and odd mass nuclei. Our calculations include deformation, binding energy, separation energy, single particle energy, root mean squared radii, along with charge and neutron density profile, etc., and are found to be an excellent match with latest experimental results demonstrating Z = 6 as a strong magic number. N = 6 is also found to have a similar kind of strong magic character. (author)
[en] Proxy-SU(3) is an approximate symmetry appearing in heavy deformed nuclei. In SDANCA-2017 the foundation of proxy-SU(3), its parameter-free predictions for the collective deformation parameters β and γ, as well as for B(E2) ratios, have been discussed and its usefulness in explaining the dominance of prolate over oblate shapes in the ground states of even-even nuclei and the point of the prolate over oblate shape transition in the rare earths region has been demonstrated. In the present contribution, preliminary calculations for two-nucleon separation energies within this framework will be discussed.
[en] Within the relativistic mean field (RMF) theory, the ground state properties of dysprosium isotopes are studied using the shell-model-like approach (SLAP), in which pairing correlations are treated with particle-number conservation, and the Pauli blocking effects are taken into account exactly. For comparison, calculations of the Bardeen-Cooper-Schrieffer (BCS) model with the RMF are also performed. It is found that the RMF+SLAP calculation results, as well as the RMF+BCS ones, reproduce the experimental binding energies and one- and two-neutron separation energies quite well. However, the RMF+BCS calculations give larger pairing energies than those obtained by the RMF+SLAP calculations, in particular for nuclei near the proton and neutron drip lines. This deviation is discussed in terms of the BCS particle-number fluctuation, which leads to the sizable deviation of pairing energies between the RMF+BCS and RMF+SLAP models, where the fluctuation of the particle number is eliminated automatically. (authors)