Shell Structure Effects Research Articles

Quantal diffusion approach for multinucleon transfers in Xe + Pb collisions

Employing a quantal diffusion description based on the stochastic mean-field (SMF) approach, we analyze the mass distribution of the primary fragments in the collisions of ${}^{136} \text{Xe}+{}^{208} \text{Pb}$ system at the bombarding energy $E_\text{c.m.} =526$~MeV. This quantal approach provides a good description of the primary fragment distribution without any adjustable parameter, including the effects of shell structure.

Atom-in-jellium equations of state in the high-energy-density regime.

Recent path-integral Monte Carlo and quantum molecular dynamics simulations have shown that computationally efficient average-atom models can predict thermodynamic states in warm dense matter to within a few percent. One such atom-in-jellium model has typically been used to predict the electron-thermal behavior only, although it was previously developed to predict the entire equation of state (EOS). We report completely atom-in-jellium EOS calculations for Be, Al, Si, Fe, and Mo, as elements representative of a range of atomic number and low-pressure electronic structure. Comparing the more recent method of pseudoatom molecular dynamics, atom-in-jellium results were similar: sometimes less accurate, sometimes more. All these techniques exhibited pronounced effects of electronic shell structure in the shock Hugoniot which are not captured by Thomas-Fermi based EOS. These results demonstrate the value of a hierarchical approach to EOS construction, using average-atom techniques with shell structure to populate a wide-range EOS surface efficiently, complemented by more rigorous three-dimensional multiatom calculations to validate and adjust the EOS.

Enhanced Bio-Electro-Fenton degradation of phenolic compounds based on a novel Fe–Mn/Graphite felt composite cathode

Phenolic compounds are problematic byproducts generated from lignocellulose pretreatment. In this study, the feasibility degradation of syringic acid (SA), vanillic acid (VA), and 4-hydroxybenzoic acid (HBA) by Bio-Electro-Fenton (BEF) system with a novel Fe–Mn/graphite felt (Fe–Mn/GF) composite cathode were investigated. The nano-scale Fe–Mn multivalent composite catalyst with core shell structure distributed more evenly on GF surface to form a catalyst layer with higher oxygen reduction reaction performance. Accordingly, the maximum power density generated with Fe–Mn/GF cathode was 48.1% and 238.9% higher than Fe/GF and GF respectively, which further enhanced the in situ generation of H2O2 due to the superiority of nano-scale core shell structure and synergistic effect of Fe and Mn species. The degradation efficiency of the three phenolic compounds in the BEF system could reached 100% after optimization of influencing parameters. Furthermore, a possible SA degradation pathway by BEF process in the present system was proposed based on the detected intermediates. These results demonstrated an efficient approach for the degradation of phenolic compounds derived from lignocellulose hydrolysates.

Impact of Outer Shell Structure and Localization Effects on Charge Carrier Dynamics in GaAs/(In,Ga)As Nanowire Core–Shell Quantum Wells

Herein, the charge carrier dynamics in GaAs/(In,Ga)As/(Al,Ga)As core–shell nanowires with different outer shell structures are studied. Localization of charge carriers in the minima of potential fluctuations is shown to govern the recombination processes at low temperatures. At higher temperatures, thermionic emission of carriers from the (In,Ga)As shell quantum well leads to a decrease of the luminescence efficiency for a sample with a GaAs outer shell. This effect can be reduced by introducing an AlAs barrier shell. However, the interfaces to this barrier act as an additional source for nonradiative recombination. These results will help in achieving high luminescence intensities at room temperature of light‐emitting devices based on nanowire shell quantum wells.

Trimetallic Au@PtPd Mesoporous Nanorods as Efficient Electrocatalysts for the Oxygen Reduction Reaction

Porous Pt-based nanostructures are highly promising electrocatalysts for fuel cells, because of their high catalytic surface area and sufficient catalytically active sites. Herein, we adopt a facile method in aqueous solution to synthesize the Au@PtPd mesoporous nanorod (Au@PtPd MNR) in which a Au nanorod (NR) serves as core, and mesoporous PtPd acts as shell. Because of the mesoporous core–shell structure and composition effect, Au@PtPd MNR exhibits superior catalytic activity and durability for the oxygen reduction reaction (ORR), as compared with PtPd mesoporous sphere (MS), Au@Pt MNR, and commercial Pt/C catalyst. This synthetic strategy is appropriate for preparation of other mesoporous core–shell structures for various promising applications.

Path integral Monte Carlo simulations of warm dense aluminum

We perform first-principles path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) calculations to explore warm dense matter states of aluminum. Our equation of state (EOS) simulations cover a wide density-temperature range of 0.1-32.4gcm^{-3} and 10^{4}-10^{8} K. Since PIMC and DFT-MD accurately treat effects of the atomic shell structure, we find two compression maxima along the principal Hugoniot curve attributed to K-shell and L-shell ionization. The results provide a benchmark for widely used EOS tables, such as SESAME, QEOS, and models based on Thomas-Fermi and average-atom techniques. A subsequent multishock analysis provides a quantitative assessment for how much heating occurs relative to an isentrope in multishock experiments. Finally, we compute heat capacity, pair-correlation functions, the electronic density of states, and 〈Z〉 to reveal the evolution of the plasma structure and ionization behavior.

Quantal diffusion description of multinucleon transfers in heavy-ion collisions

Employing the stochastic mean-field (SMF) approach, we develop a quantal diffusion description of the multi-nucleon transfer in heavy-ion collisions at finite impact parameters. The quantal transport coefficients are determined by the occupied single-particle wave functions of the time-dependent Hartree-Fock equations. As a result, the primary fragment mass and charge distribution functions are determined entirely in terms of the mean-field properties. This powerful description does not involve any adjustable parameter, includes the effects of shell structure and is consistent with the fluctuation-dissipation theorem of the non-equilibrium statistical mechanics. As a first application of the approach, we analyze the fragment mass distribution in $^{48}\mathrm{Ca}+{}^{238}\mathrm{U}$ collisions at the bombarding energy $E_{\text{c.m.}}=193$ MeV and compare the calculations with the experimental data.

Facile synthesis of one-dimensional hollow Sb2O3@TiO2 composites as anode materials for lithium ion batteries

Metallic Sb is deemed as a promising anode material for lithium ion batteries (LIBs) due to its flat voltage platform and high security. Nevertheless, the limited capacity restricts its large-scale application. Therefore, a simple and effective method to explore novel antimony trioxide with high capacity used as anode material for LIBs is imperative. In this work, we report a facile and efficient strategy to fabricate 1D hollow Sb2O3@TiO2 composites by using the Kirkendall effect. When used as an anode material for LIBs, the optimal Sb2O3@TiO2 composite displays a high reversible discharge capacity of 593 mAh g−1 at a current density of 100 mA g−1 after 100 cycles and a relatively superior discharge capacity of 439 mAh g−1 at a current density of 500 mA g−1 even after 600 cycles. In addition, a reversible discharge capacity of 334 mAh g−1 can also be obtained even at a current density of 2000 mA g−1. The excellent cycling stability and rate performance of the Sb2O3@TiO2 composite can be attributed to the synergistic effect of TiO2 shell and hollow structure of Sb2O3, both of which can effectively buffer the volume expansion and maintain the integrity of the electrode during the repeated charge-discharge cycles.

Effect of the Semiconductor Quantum Dot Shell Structure on Fluorescence Quenching by Acridine Ligand

The main line of research in cancer treatment is the development of methods for early diagnosis and targeted drug delivery to cancer cells. Fluorescent semiconductor core/shell nanocrystals of quantum dots (e.g., CdSe/ZnS) conjugated with an anticancer drug, e.g., an acridine derivative, allow real-time tracking and control of the process of the drug delivery to tumors. However, linking of acridine derivatives to a quantum dot can be accompanied by quantum dot fluorescence quenching caused by electron transfer from the quantum dot to the organic molecule. In this work, it has been shown that the structure of the shell of the quantum dot plays the decisive role in the process of photoinduced charge transfer from the quantum dot to the acridine ligand, which is responsible for fluorescence quenching. It has been shown that multicomponent ZnS/CdS/ZnS shells of CdSe cores of quantum dots, which have a relatively small thickness, make it possible to significantly suppress a decrease in the quantum yield of fluorescence of quantum dots as compared to both the classical ZnS thin shell and superthick shells of the same composition. Thus, core/multicomponent shell CdSe/ZnS/CdS/ZnS quantum dots can be used as optimal fluorescent probes for the development of systems for diagnosis and treatment of cancer with the use of anticancer compounds based on acridine derivatives.

Electron and Nucleon Localization Functions of Oganesson: Approaching the Thomas-Fermi Limit.

Fermion localization functions are used to discuss electronic and nucleonic shell structure effects in the superheavy element oganesson, the heaviest element discovered to date. Spin-orbit splitting in the 7p electronic shell becomes so large (∼10 eV) that Og is expected to show uniform-gas-like behavior in the valence region with a rather large dipole polarizability compared to the lighter rare gas elements. The nucleon localization in Og is also predicted to undergo a transition to the Thomas-Fermi gas behavior in the valence region. This effect, particularly strong for neutrons, is due to the high density of single-particle orbitals.

Theoretical investigation of existence of meta-stability in iron and cobalt clusters

Nowadays considerable attention has been given for researches on magnetic properties of transition metal clusters (specifically FeN and CoN). This is because these clusters offer big hopes for the possibility of presenting significant magnetic anisotropy energy which is critical for technological applications. This study intends to find out the causes for the existence of the two states (ground and meta-stable) in Iron and Cobalt clusters. The study also explains the role of valence electrons for the existence of magnetism in the two states by using the concept of ionization potential, electron dipole polarizabilities, chemical hardness and softness of the clusters. Assuming that, when all itinerant electrons are at s-level and also at the d-level (ns=nandns→0.) the ground state and meta-stable state energies with distinct energy minima are (Egs=l/2n+εcn−2μBhnandEms=εdn−gμBhn) respectively. The findings also showed that polarizability of small cluster of the specified elements are increased compared with the bulk value, which means that there is an effective increase in the cluster radius due to the spilling out of the electronic charge. Furthermore, it is obvious that 4s electrons are more delocalized than the 3d electrons so that they spill out more than the 3d electrons. This leads to the conclusion that 4s electrons are primarily responsible for the enhanced polarizabilities and for shell structure effects. This indicates that polarizability at the meta-stable state is less than that of the ground state i.e. the meta-stable state loses its s electron. Therefore the two minima represent a ground state of configuration 3d↑53d↓2+δ4s2−δ with energy Egs and meta-stable state of configuration 3d↑53d↓3+δ4s1−δ with energy Ems for Co clusters and a ground state configuration 3d↑53d↓1+δ4s2−δ with energy Egs an meta-stable state of configuration 3d↑53d↓2+δ4s1−δ with energy Ems for Fe clusters. Hence, the existence of the two states (meta-stable & ground state) is due to the large disproportion in electronic configurations of the two clusters at their respective states. Furthermore, the chemical hardness and softness of the clusters also provide evidence for the existence of stability of the two states depending on the cluster size.

First-principles simulations of warm dense lithium fluoride.

We perform first-principles path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) calculations to explore warm dense matter states of LiF. Our simulations cover a wide density-temperature range of 2.08-15.70gcm^{-3} and 10^{4}-10^{9} K. Since PIMC and DFT-MD accurately treat effects of atomic shell structure, we find a pronounced compression maximum and a shoulder on the principal Hugoniot curve attributed to K-shell and L-shell ionization. The results provide a benchmark for widely used EOS tables, such as SESAME, LEOS, and models. In addition, we compute pair-correlation functions that reveal an evolving plasma structure and ionization process that is driven by thermal and pressure ionization. Finally, we compute electronic density of states of liquid LiF from DFT-MD simulations and find that the electronic gap can remain open with increasing density and temperature to at least 15.7 gcm^{-3}.

Calculation of Reactions Cross Section for Neutron-Induced Reactions on <sup>127</sup>I Isotope

In this work, the reaction cross-section for neutron-induced reactions on 127I isotope was calculated using EXIFON code in the energy range of incident particle from 0 MeV to 30 MeV. The code is based on an analytical model for statistical multistep direct and multistep compound reactions (SMD/SMC model). In order to see the effect of nuclear structure on cross sections, the calculation was done using nuclear shell structure effect and without considering shell structure effect. Obtained results and statistical analysis showed that shell structure effect does not give significant changes to the cross-section at considered energy ranges. This shows that EXIFON code is a good tool for investigation of nuclear reaction cross section and is useful in the production of the radioisotopes of Iodine, Antimony and tellurium of high purity and in an efficient manner using cyclotron or nuclear reactors, these isotopes have potential application for field of medical science especially for diagnostics and therapeutic purposes.

The nucleon localization function in static and time-dependent DFT

Static and time-dependent density functional theory (DFT) calculations are often used to predict fission fragment distributions or fusion cross sections with great success. However, nuclear shell structure and clusterization effects are usually studied using the density distribution of the nucleons which is a poor indicator of these phenomena. In this work, we employ a measure called the localization function, which was first introduced in chemistry to visualize electronic bonds and recently applied to nuclear physics for light nuclei to reveal α-clustering. We show, that the localization function reveals the shell structure of the fragments in fission long before the scission point and also illustrates the shell structure of intermediate states in time-dependent DFT calculations.

Evaluation of Excitation Functions of Reactions Used in Production of Some Medical Radioisotopes

In this work, reaction cross-sections were calculated and Excitation Functions were evaluated for productions of 208Bi, 212,211,210At, 211,210Po isotopes using EXIFON code in the energy range from 0 MeV to 30 MeV. The code is based on an analytical model for statistical multistep direct and multistep compound reactions (SMD/SMC model). This work also investigates the shell structure effect on the reaction cross-section, the results obtained show that the cross-sections of (a, na) reaction for both with shell correction and without shell correction are zeros at energies range considered, this shows that the energy of the incident particle is below the threshold of this reaction due to the present of coulomb repulsive force between the projectile and target nucleus.

Charge Radii of Neutron Deficient ^{52,53}Fe Produced by Projectile Fragmentation.

Bunched-beam collinear laser spectroscopy is performed on neutron deficient ^{52,53}Fe prepared through in-flight separation followed by a gas stopping. This novel scheme is a major step to reach nuclides far from the stability line in laser spectroscopy. Differential mean-square charge radii δ⟨r^{2}⟩ of ^{52,53}Fe are determined relative to stable ^{56}Fe as δ⟨r^{2}⟩^{56,52}=-0.034(13) fm^{2} and δ⟨r^{2}⟩^{56,53}=-0.218(13) fm^{2}, respectively, from the isotope shift of atomic hyperfine structures. The multiconfiguration Dirac-Fock method is used to calculate atomic factors to deduce δ⟨r^{2}⟩. The values of δ⟨r^{2}⟩ exhibit a minimum at the N=28 neutron shell closure. The nuclear density functional theory with Fayans and Skyrme energy density functionals is used to interpret the data. The trend of δ⟨r^{2}⟩ along the Fe isotopic chain results from an interplay between single-particle shell structure, pairing, and polarization effects and provides important data for understanding the intricate trend in the δ⟨r^{2}⟩ of closed-shell Ca isotopes.

Overpressure peak formula of surface shock waves in single layer spherical lattice shell under the effect of internal explosion

This paper uses the LS-DYNA analysis software to make numerical simulation and analysis on the blast effect of single layer spherical lattice shell structure under the action of internal explosion, summarized overpressure peak distribution characteristics of surface shock waves in lattice shell under internal explosion: shock waves overpressure peak of lattice shell top is mainly secondary wave overpressure peak, while at rest locations, it is mainly first wave overpressure peak; shock waves overpressure peak distribution in lattice shell and side wall is big at both ends and small in the middle. Finally, according to distribution law of shock waves overpressure peak, we proposed simplified calculation formula for surface shock waves overpressure peak in singer layer spherical lattice shell, to provide reference for antiknock and explosion-proof of engineering structures.

Structures of Nanoalloy Clusters AunAln(n= 1–10) and the Growth Patterns to the Bulk Phase

Gold nanoclusters have attracted intense interests due to their unique applications as catalysts. The properties of the gold clusters can often be extended through alloying with other metals, by virtue of adding new degrees of freedom and increasing the versatility of bonding. Here, we reported a new series of bimetallic clusters AunAln (n = 1–10) determined from the density functional calculations. Particle swarm global minimum searches, coupled with density functional optimization, were used to identify low-lying structures of the AunAln clusters and the crystalline phase, in addition to the experimentally known AuAl and Au2Al2 structures. Significantly enhanced binding energies were calculated in stable AunAln clusters compared with their pure Au or Al counterparts as a result of polarized Au–Al interactions. The polarization is due to a high electron affinity of gold induced by strong relativistic and shell structure effects. In addition, an Au2Al2 unit was identified as the common motif for lowest-en...

SKELETAL EMBRYONIC DEVELOPMENT AND HATCHING TRAITS AS AFFECTED BY EGGSHELL OSTEOPONTIN PROTEIN DURING TWO STAGES OF EGG LAYING CYCLE

The present experiment was carried out for determining the role of osteopontin protein (OPN) in eggshell on shell quality and consequent effect on skeletal embryos, hatching traits and some physiological parameters besides its relation with two stages of laying cycle of Mandarah chickens (32 to42 vs 52 to 62 wks. of age). The obtained results are summarized as follows:- Osteopontin concentrations (ng/µL) were decreased (P≤0.05) for eggshell of fresh eggs and hatched chicks for eggs produced from elder chickens compared with those from younger ones. The same trend of significant decrease of OPN was observed for tibia of hatched chicks and for chick's blood. Osteopontin concentration decreased (P≤0.05) with the increase of embryonic age with respect to eggshell whereas, it increased for tibia. Younger chickens represented significant increase of eggshell strength, eggshell index, eggshell and eggshell membranes thickness compared to those for elder ones. Embryonic mortality %, hatch time (hr) and chick body weight at pull out (g) were significantly increased for eggs produced from elder chickens compared to those for younger ones while, hatchability of fertile eggs % was significantly decreased. Calcium and phosphorus values were significantly decreased with the increase of flock age for eggshell of fresh eggs and eggshell through different times of incubation besides tibia of embryos at 15th day and for chicks at hatch. Blood constituents of hatched chicks as calcium, phosphorus, and parathyroid hormone were significantly decreased with the increase of chicken age. Relative asymmetry is higher (P≤0.05) for wing, tibia, tarsus and femur lengths of embryos and baby chicks for younger flock compared to elder one except that for tarsus of baby chicks. The contributions of OPN as a major protein in shell structure and subsequent effects on hatching process are proven and this conclusion could set up alternative tool for eggshell quality evaluation and breeding selection programs.

Effect of shell structure on neutron multiplicity of fissioning systems220,222,224Th nuclei

The pre- and post-scission neutron multiplicities have been extracted for the 220,222,224Th nuclei for the excitation energy range of 40 MeV to 64 MeV using the National Array of Neutron Detectors (NAND). The Th isotopes are populated from the fusion reaction of 16O+204,206,208Pb systems in order to investigate the dynamics of fusion-fission reactions using the neutron multiplicity as a probe. The theoretical calculations were performed using the Bohr-Wheeler fission width as well as the dissipative dynamical fission width from Kramers prescription. It is observed that the Bohr-Wheeler fission width underestimates the pre-scission yields to a large extent. A large amount of dissipation is required in the Kramers width to fit the observed pre-scission neutron multiplicities.