Fermi Density Research Articles

Optimization of Carbon-Defect Engineering to Boost Catalytic Ozonation Efficiency of Single Fe─N4 Coordination Motif.

Carbon-defect engineering in single-atom metal-nitrogen-carbon (M─N─C) catalysts by straightforward and robust strategy, enhancing their catalytic activity for volatile organic compounds, and uncovering the carbon vacancy-catalytic activity relationship are meaningful but challenging. In this study, an iron-nitrogen-carbon (Fe─N─C) catalyst is intentionally designed through a carbon-thermal-diffusion strategy, exposing extensively the carbon-defective Fe─N4 sites within a micro-mesoporous carbon matrix. The optimization of Fe─N4 sites results in exceptional catalytic ozonation efficiency, surpassing that of intact Fe─N4 sites and commercial MnO2 by 10 and 312 times, respectively. Theoretical calculations and experimental data demonstrated that carbon-defect engineering induces selective cleavage of C─N bond neighboring the Fe─N4 motif. This induces an increase in non-uniform charges and Fermi density, leading to elevated energy levels at the center of Fe d-band. Compared to the intact atomic configuration, carbon-defective Fe─N4 site is more activated to strengthen the interaction with O3 and weaken the O─O bond, thereby reducing the barriers for highly active surface atomic oxygen (*O/*OO), ultimately achieving efficient oxidation of CH3SH and its intermediates. This research not only offers a viable approach to enhance the catalytic ozonation activity of M─N─C but also advances the fundamental comprehension of how periphery carbon environment influences the characteristics and efficacy of M─N4 sites.

Well-dressed repulsive-core solitons and nonlinear optics of nuclear reactions

We introduce the concept of nonlinear optics of nuclear reactions and reveal a deep analogy between nonlinear dynamics of the so-called “well-dressed repulsive-core” solitons and the nuclear reactions that take place among atomic nuclei. We derive a nonlinear evolution equation for the Fermi nuclear density and the Woods–Saxon potential based on the inverse problem in the diffraction and dispersion scattering. We obtain a simple formula for the self-interaction (binding) energy, which provides the shape and structural stability of “soliton-like nucleus” with the Fermi density distribution. We find the shape squareness parameter (edge steepness) for “soliton-like nucleus” density distribution and demonstrate its specific quantization related to the conservation of the total number of nucleons. The shape squareness parameter plays a decisive role in increasing the binding soliton energy and appearing the oscillatory side-band spectral structures responsible for the fusion and fission reactions with soliton-like nuclei. We hope that nonlinear-optical analogies found in our work will be able to shed additional light on the fundamental problems of stellar nucleosynthesis. We support our findings with concrete examples of fusion and fission reactions with “well-dressed repulsive-core” nucleus-like solitons: the carbon and oxygen-burning processes, the iron-synthesis, and nuclear fusion–fission reactions induced by alpha particles.

Cation Substitution Induced d‐Band Center Modulation on Cobalt‐Based Spinel Oxides for Catalytic Ozonation

AbstractCo3O4 spinel is a promising transition metal oxide (TMO) catalyst for the catalytic ozonation of volatile organic compounds (VOCs). Herein, metal–organic frameworks (MOFs)‐derived Ni‐ and Mg‐ substituted Co3O4 catalysts retain similar spinel structures, but display improved and reduced ozonation performance of methyl mercaptan (CH3SH), respectively. Remarkably, the NiCo2O4 catalyst can still ≈90% removal of CH3SH after running for 20 h at room temperature under an initial concentration of 50 ppm CH3SH and 40 ppm O3, relative humidity of 60%, and space velocity of 300 000 mL h−1 g−1, exceeding the reported values. Experimental characterizations have unveiled that the substitution of Ni and Mg into the Co3O4 spinel altered surface acidity, oxygen species mobility, and Co2+/Co3+ ratio. The in situ Raman spectra reveal the dynamic formation Co(III)‐Oad* via the transformation of O3 into surface atomic oxygen (Oad*) and peroxide species (O2*). Theoretical calculations verify that Ni‐substitution increases nonuniform charges and Fermi density, leading to a moderate increase in d‐band center energy levels, thereby promoting O3 specific adsorption/activation to convert Oad*/O2* and •OH/1O2/•O2−, which contributes to eliminate CH3SH and prevent poisoning. The concept of tuning the d‐band center can provide valuable insights for the design of other catalysts for catalytic ozonation.

Matter density distributions of Ne20,22 and Mg24,26 extracted through proton elastic scattering at 0.8 GeV

Reported small-angle differential cross sections of proton elastic scattering off $^{20,22}\mathrm{Ne}$ and $^{24,26}\mathrm{Mg}$ at 0.8 GeV were analyzed with the Glauber model. Matter density distributions of $^{20,22}\mathrm{Ne}$ and $^{24,26}\mathrm{Mg}$ were determined based on the two-parameter Fermi density model, and the corresponding root-mean-square point-matter radii are 2.891(52) fm, 2.895(104) fm, 2.935(20) fm, and 2.946(21) fm. The occupation number effects of the $2s$ orbital on inner density were probed by the matter density difference between $^{22}\mathrm{Ne}$ and $^{24}\mathrm{Mg}$. Combined with the experimental occupation numbers, the relativistic Hartree-Bogoliubov calculations with the DD-ME2 and PC-PK1 interactions describe the obtained density difference trend, and indicate that there may be a bubble structure in $^{24}\mathrm{Mg}$.

Quarkyonic mean field theory

We discuss mean field theory of quarkyonic matter at zero temperature. We treat the nucleons with contact interactions in mean field approximation, discussing both vector and scalar mean field interactions. We treat the quarks without mean field vector interactions, but allow mass terms to be generated consistently from a scalar mean field consistent with the additive quark model for quark masses. Quarkyonic matter is composed of a shell of nucleons that under-occupy the total available phase space associated with the underlying quark degrees of freedom. The fully occupied Fermi sphere beneath this shell of nucleons at high densities is thought of as quarks, but when this fully occupied distribution of states first appears, although the phase space is filled, the matter is at low density. For the transition between this low density and high density saturated matter, we advocate a dual description of the fully filled Fermi sea in terms of hadrons, and make a phenomenological hypothesis for the equation of state of this matter. We then proceed to an example where the mean field interactions are all vector and only associated with the nucleons, ignoring the effects of mass change associated with the scalar interactions. Except for the effects of Pauli blocking, the nucleons and quarks do not interact. To get a reasonable transition to quarkyonic matter the interaction of the quarks among themselves are assumed to be nonperturbative, and a simple phenomenological relation between quark Fermi energy and density is introduced.

Mobile ion in a Fermi sea

The remarkable single particle control of individual ions combined with the versatility of ultracold atomic gases makes hybrid ion-atom system an exciting new platform for quantum simulation of few- and many-body quantum physics. Here, we study theoretically the properties of a mobile ion immersed in a quantum degenerate gas of fermionic atoms. Using an effective low-energy atom-ion interaction together with a well established approach that includes exactly two-body correlations, we calculate the full spectral response of the ion and demonstrate the existence of several quasiparticle branches, which are charged analogues of the Fermi polaron observed in neutral atomic gases. Due to the long-range nature of the atom-ion interaction, these ionic Fermi polarons have several properties distinct from their neutral counterparts such as the simultaneous presence of several stable states and smooth transitions from repulsive to attractive polarons with increasing interaction strength. Surprisingly, the residue of the ionic polaron is shown to increase with the Fermi density for fixed interaction strength, which is in marked contrast to the neutral polaron. The properties of the ionic polaron approach that of the neutral polaron only in the low density limit where the average interparticle spacing is larger than the characteristic length of the atom-ion interaction. We finally analyse the effects of the Fermi gas on the molecular ions, which are bound atom-dimer states.

Enormous nuclear surface diffuseness of Ne and Mg isotopes in the island of inversion

Background: The density profile of exotic nuclei can be a rich source of information on the nuclear surface. In particular, the nuclear surface diffuseness is correlated with the occupation probability of nucleons in distinct nuclear orbits, especially those with low angular momenta.Purpose: The aim of this paper is to investigate the relationship between the nuclear surface diffuseness and spectroscopic information of neutron-rich Ne and Mg isotopes both at the cusp and inside the island of inversion.Method: We use the microscopic antisymmetrized molecular dynamics model to calculate the densities and other spectroscopic information related to Ne and Mg isotopes. A two-parameter Fermi density distribution is then used to define the diffuseness parameter and the matter radius. These quantities are extracted by minimizing the difference between these two densities. To relate them with observables, the two densities are given as inputs to a Glauber model calculation of nucleon-nucleus elastic scattering differential cross section, with the demand that they reproduce the first peak position and its magnitude.Results: A marked increase in the occupation of neutrons in the $pf$ orbit is noted in Ne and Mg isotopes from $N=19$ onwards. We observed that the nuclear surface diffuseness is strongly correlated with the nuclear deformation, in the island of inversion, and gradually increases with the occupation of neutrons in the $1{p}_{3/2}$ orbit. This result is also confirmed by a single-particle estimate of the valence neutron density distribution, with $^{29}\mathrm{Ne}$ as a test case. An exception is noted for $^{35--37}\mathrm{Mg}$, where the filling up of the holes in the $sd$ shell partially compensates the increase in diffuseness due to filling up of the $1{p}_{3/2}$ orbit.Conclusion: Information on nuclear density profile of neutron-rich medium mass nuclei can be reliably extracted by studying the first diffraction peak of the nucleon-nucleus elastic scattering differential cross section. The enormous surface diffuseness of Ne and Mg isotopes, in the island of inversion, could be attributed to the increasing neutron occupation of the $1{p}_{3/2}$ orbit.

Manipulation of crystalline structure, magnetic performance, and topological feature in Mn3Ge films

The Mn3X (where X = Ga, Ge, Sn, etc.) compounds have appealing prospects for spintronic applications due to their various crystal structures and magnetic properties for the design of reliable high-density memories. However, controlled growth of high-quality Mn3X thin films remains challenging in material science. Here, we reported the controlled film growth of Heusler alloy Mn3Ge, which could crystallize in respective tetragonal and hexagonal structures. The tetragonal D022-type Mn3Ge film exhibits strong perpendicular ferromagnetic anisotropy, while the hexagonal D019-type Mn3Ge film indicates non-collinear triangular antiferromagnetic order. From our experimental observations of structure characterizations, magnetic properties, anomalous Hall effect, and magnetoresistance measurements, we realized the manipulation of spin orientations and topological features. Majority/minority spin polarized Fermi surface and density of states of both tetragonal and hexagonal Mn3Ge structures were investigated by density functional theory calculations. Our work not only opens up technology routes toward the development of Mn3X-based devices for applications in topological spintronics and spin-torque memories but also leads to engineer the physical properties for fundamental study.

Fabrication of Ge<sub>30</sub>Te <sub>70-x</sub>Sb<sub>x</sub> Glasses Alloys and Studying the Effect of Partial Substitution on D.C Electrical Energy Parameters

The non-linear components has been emphasized for its multiple applications in rewritable recording and data storage devices. Chalcogenide glasses materials are promising due to their high refractive index. In this paper, alloys for Ge30Te70-xSbxglasses semiconductor (where x =0.0, 5, 10, 15 and 20) will be fabricated by melt quenching method. The effect of partial substitution on DC electric power parameters, and its knowledge of electrical conduction mechanisms, were investigated to determine the effect of Antimony on the density of extended states, local states, and in Fermi energy states. The electrical measurements revealed the existence of three conduction mechanisms depend on the temperature: at high temperature the conduction will be in the extended state. The local states are responsible at medium temperature, and at low temperature it will related to the Fermi level. The effect of partial substitution had produced change in all electrical conductivity parameters including the (extended, localized, and Fermi) density of states, the activation energy, tail width (ΔE), hoping transition distance (R), and interatomic distances a.

Incorporation of copper nanoparticles into the nitrogen‐doped carbon derived from nitrile functionalized ionic liquid as the non‐precious heterogeneous catalytic system toward nitro compounds reduction reaction, a first principle calculation

AbstractBACKGROUNDToday, Nitrogen‐doped carbon materials have gained attention as the robust solid catalyst support for immobilization nanoparticles to expand the heterogeneous catalytic systems due to their chemical and structural stability. Copper nanoparticles, known to be a cost‐effective metal, are one of the most efficient catalyst toward various organic transformations.RESULTSIn this paper, the covalent triazine framework mesoporous solid support was successfully fabricated by applying ionic liquid as a nitrogen containing carbon precursor during the ionothermal process with the help of ZnCl2 molten salt at 400 °C. The immobilization of cost‐effective copper nanoparticles on the surface of the new design support was carried out by using Cu (NO3)2 and N2H4. For characterization of the new heterogeneous catalyst, the combination of different physicochemical analyses was done to confirm the successful preparation of catalyst inclusive Fourier transform infrared spectroscopy, X‐ray diffraction, Field emission scanning electron microscopy, N2 adsorption–desorption isotherm, Raman spectroscopy, and thermogravimetric analysis. Besides, DFT (Density functional theory) calculations have been performed to optimize the constructed structures and to calculate their Fermi levels and density of states.CONCLUSIONThe catalytic capability of this new design catalyst survived in hydrogenation of nitroarenes under aqueous and mild conditions. The result shows that this new heterogeneous mesoporous catalyst has excellent catalytic activity and a high stability towards nitroarenes hydrogenation reaction. Moreover, due to the high stability (thermal and structural), it was recovered and reused up to 7 times without any significant reduction in its catalytic activity. © 2021 Society of Chemical Industry (SCI).

Elastic Scattering with Double Folding Model: 8B+27Al

In the present work, the elastic scattering of the 8B+27Al reaction at two different energies have been examined using the microscopic double folding potential approximation within the framework of the optical model. The real part of the optical model has been obtained by using Fermi, Gaussian and Variational Monte Carlo (VMC) density distributions in the microscopic double folding model and the imaginary part has been taken as Woods-Saxon volume type. The results of our microscopic analysis are quite compatible with the experimental cross-section data. The reaction cross sections, the volume integrals of used potentials and their χ2/N errors have also been computed. This study is important in showing the effect of microscopically derived potentials in explaining the 8B+27Al experimental data published recently.

Surface Modification and Subsequent Fermi Density Enhancement of Bi(111).

Defects introduced to the surface of Bi(111) break the translational symmetry and modify the surface states locally. We present a theoretical and experimental study of the 2D defects on the surface of Bi(111) and the states that they induce. Bi crystals cleaved in ultrahigh vacuum (UHV) at low temperature (110 K) and the resulting ion-etched surface are investigated by low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) as well as spectroscopy (STS) techniques in combination with density functional theory (DFT) calculations. STS measurements of cleaved Bi(111) reveal that a commonly observed bilayer step edge has a lower density of states (DOS) around the Fermi level as compared to the atomic-flat terrace. Following ion bombardment, the Bi(111) surface reveals anomalous behavior at both 110 and 300 K: Surface periodicity is observed by LEED, and a significant increase in the number of bilayer step edges and energetically unfavorable monolayer steps is observed by STM. It is suggested that the newly exposed monolayer steps and the type A bilayer step edges result in an increase to the surface Fermi density as evidenced by UPS measurements and the Kohn–Sham DOS. These states appear to be thermodynamically stable under UHV conditions.

Phenomenological nuclear density distributions

A recently proposed semiphenomenological density distribution for neutrons and protons in nuclei is discussed. This density was derived using the separation energies of the last neutron or proton. A com­parison is made with the symmetrised Fermi density distribution with parameters determined by fitting electron scattering experimental data and with a Fermi density with parameters coming from a recent anal­ysis of pionic atoms. Theoretical expressions for rms radii for neutron, proton and matter distributions are proposed, which give the average trend of the variation of these quantities as functions of Ν, Ζ and A respectively. To facilitate the use of the new density all the parameters needed in a practical application are tabulated for a series of nuclei. Some applications of the new density are also discussed.

Analysis of the barrier characteristics and related fusion properties using 2pF, 3pF and 3pG density functions

The role of three-parameter Fermi (3pF) and three-parameter Gaussian (3pG) density functions on the fusion dynamics has been explored in comparison to the two-parameter Fermi (2pF) within the semiclassical Skyrme Energy Density Formalism. For the case of the three-parameterized density functions (3pF and 3pG), an additional parameter ‘w’ influences the tail and nearby region, and hence the barrier characteristics get modified accordingly. In view of this, the role of 2pF, 3pF and 3pG density functions has been analyzed by calculating the fusion barrier height VB (and barrier position RB) for a variety of nuclear reactions with the mass-asymmetry spread from symmetric to extreme asymmetric reaction partners, and the results are compared with the available data. In addition to this, the fusion cross-sections for 58Ni-based reactions are also calculated using extended ℓ-summed Wong model and the collective effect of VB, RB and ħωB (barrier height, position and curvature respectively) for the use of above mentioned density distributions has been examined. It is found that 2pF density functional is more suitable for symmetric reactions, whereas 3pF and 3pG seems to be appropriate for asymmetric reactions.

Improving the HER activity of Ni3FeN to convert the superior OER electrocatalyst to an efficient bifunctional electrocatalyst for overall water splitting by doping with molybdenum

Developing efficient and earth-abundant bifunctional electrocatalyst for overall water splitting to produce hydrogen is very important. Ni3FeN is always used as an excellent electrocatalyst for the oxygen evolution reaction (OER), but its hydrogen evolution reaction (HER) performance is always negative and seldom concerned. Here, we improve the HER activity and maintain the excellent OER activity of Ni3FeN to realize the efficient overall water splitting by doping with molybdenum. The Mo-doped Ni3FeN shows a significantly improved HER activity with a low overpotential of 69 mV at 10 mA cm−2 as well as an excellent OER activity with a low overpotential of 250 mV at 20 mA cm−2. The improved HER activity can be ascribed to the favorable absorption/desorption process of H intermediate and improved conductivity, which was verified by the density functional theory calculation results of free energy of adsorbed H (ΔGH*), the position of d-band center toward Fermi level and density of state near Fermi level. A two-electrode system that has Mo-doped Ni3FeN electrode as both cathode and anode requires only a low cell voltage of 1.554 V to reach the current density of 10 mA cm−2 and exhibits good stability for overall water splitting. The two-electrode system can also be powered by a commercial AA battery (∼1.5 V), which is better than most of the bifunctional electrocatalysts.

Quantum effects in bi-dust plasmas

In this paper a theoretical approach has been carried out using a fluid model on a bi-dust plasma which consist of two dusts negative charged different particles in an electron–ion plasma. In such system, this fluid model describe a dense strong coupled heavy dust grain together with a weak coupled light dusty particle. The bulk is immersed in a system of electrons and ions dominated by a Thomas–Fermi density distribution, where interaction and propagation of solitary dust acoustic solitary waves will be analyzed. This investigation will be carried out for arbitrary amplitude of solitary dust acoustic waves. These are originated through the presence of both dust grains in the plasma system. Therefore, it is used a set of fluid equation which determine general expressions for the concentrations of different dust particles. The onset of the Sagdeev method is then employed in order to look for influence of the light component on the quantum system. In this way there is an increasing or decreasing in the Sagdeev potential. This is a quantum effect phenomena.

Superconductivity in Ru-doped CuIr2Te4 telluride chalcogenide

Here we report the effect of structural and superconductivity properties on Ru doped CuIr2Te4 telluride chalcogenide. XRD results suggest that the CuIr2-xRuxTe4 maintain the disordered trigonal structure with space group P3m1 (No. 164) for x less than 0.3. The lattice constants, a and c, both decrease with increasing Ru content. Temperature-dependent resistivity, magnetic susceptibility and specific-heat measurements are performed to characterize the superconducting properties systematically. Our results suggest that the optimal doping level for superconductivity in CuIr2-xRuxTe4 is x = 0.05, where Tc is 2.79 K with the Sommerfeld constant gamma of 11.52 mJ mol-1 K-2 and the specific-heat anomaly at the superconducting transition, is approximately 1.51, which is higher than the BCS value of 1.43, indicating CuIr1.95Ru0.05Te4 is a strongly electron-phonon coupled superconductor. The values of lower critical filed and upper critical field calculated from isothermal magnetization and magneto-transport measurements are 0.98 KOe and 2.47 KOe respectively, signifying that the compound is clearly a type-II superconductor. Finally, a dome-like shape superconducting Tcs vs. x content phase diagram is established, where the charge density wave disappears at x = 0.03 while superconducting transition temperature (Tc) rises until it reaches its peak at x = 0.05, then, with decreasing when x reaches 0.3. This feature of the competition between CDW and the superconductivity could be caused by tuning the Fermi surface and density of states with Ru chemical doping.

First-principles study of the electronic structure and the Fermi surface in rare-earth filled skutterudites RPt4Ge12

Experiments on rare-earth filled skutterudites demonstrate an intriguing array of thermodynamic, transport and superconducting properties, and bring to fore theoretical challenges posed by f-electron systems. First principle calculations based density functional theory and its extensions for strongly correlated systems such as the Hubbard U correction, provide valuable information about electronic structure that can be used to understand experiments. We present a comprehensive study of the electronic structure and Fermi surface of a series of rare earth filled skutterudites, RPt4Ge12 (where R = La, Ce, Pr), aimed at shedding light on: consequences of progressive increase of f-orbital occupancy in the series; the effects of the Hubbard parameter U; the Fermi surfaces, band structures and densities of states. The calculated Fermi surfaces may be relevant to the question of multi-band versus single-band superconductivity. Computed densities of states qualitatively explain the available resonant photoemission spectroscopy experiments, and (together with available specific heat measurements) provide estimates of the effective masses. We also show the existence of pseudogaps in the total density of states which may be relevant for the thermoelectric properties of these systems.

First-principles quantum corrections for carrier correlations in double-layer two-dimensional heterostructures

We present systematic ab initio calculations of the charge carrier correlations between adjacent layers of two-dimensional materials in the presence of both charged impurity and strain disorder potentials using the examples of monolayer and bilayer graphene. For the first time, our analysis yields unambiguous first-principles quantum corrections to the Thomas--Fermi densities for interacting two-dimensional systems described by orbital-free density functional theory. Specifically, using density-potential functional theory, we find that quantum corrections to the quasi-classical Thomas-Fermi approximation have to be taken into account even for heterostructures of mesoscopic size. In order for the disorder-induced puddles of electrons and holes to be anti-correlated at zero average carrier density for both layers, the strength of the strain potential has to exceed that of the impurity potential by at least a factor of ten, with this number increasing for smaller impurity densities. Furthermore, our results show that quantum corrections have a larger impact on puddle correlations than exchange does, and they are necessary for properly predicting the experimentally observed Gaussian energy distribution at charge neutrality.

Analysis of the reaction cross-sections of 22−36Na+12C and 19−27F+12C at 240MeV/u

The nucleus–nucleus reaction cross-sections of [Formula: see text]C and [Formula: see text]C at 240[Formula: see text]MeV/u are calculated using the optical limit of the Glauber model. The deformation and radii of a deformed Fermi density are calculated from the relativistic mean field (RMF). The results are compared with the recent experimental data. It is found that the Fermi density whose quadrupole deformation parameters and radii are derived from RMF, using TMA effective interaction in the RMF Lagrangian, provide a satisfactory explanation of the experimental data of Na isotopes, except for [Formula: see text]Na, which are expected to be strongly deformed. For F isotopes, the deformed Fermi density adjusted to the radii derived from RMF, using TMA interaction, presents a lower reaction cross-section. The Lagrangian parameters set NL3* gives a good description of the data which is better than that predicted by TMA. On the other hand, the two forces cannot describe the reaction cross-section of [Formula: see text]F since it is expected to have a deformed halo structure. The radius deduced from the data is found to be of the order 3.5[Formula: see text]fm.