Interelectron Interaction Research Articles

Effect of 3d-transition metal ions on the structural, optical and magnetic properties of chromium-bearing barium borate glass

This article reports the effect of 3d-transition metal ions on the optical features of chromium ions bearing glass host. Interestingly, this study unveiled the charge transfer of Cr ions at high energy (at 347 nm), which is often hidden in earlier reports due to its vicinity to the glass edge, and its immersion in the lattice band of the glass host. In addition to the well-defined charge transfer at low energy (at 378 nm). In this vein, glass composition [(TM)1−(B2O3)80−(BaO)18.7−(Cr2O3)0.3], where TM is the transition metal ions in their oxide form, was prepared via the melt-quenching method at about 1100 °C. X-ray diffraction patterns confirmed the amorphous structure of the glass, and the chemical composition was examined using energy-dispersive X-ray spectra. The decrease in density (from 2.74 gcm−3 to 2.59 gcm−3) and the increase in molar volume (from 31.92 cm3mol−1 to 34.32 cm3mol−1) were demonstrated. Moreover, the refractive index is attained at an average value (1.50). The glass structure was studied using infrared spectroscopy, which elucidated an increase in N4 (33.2%–37.5 %) and an increase in NBO (15.3%-18.4 %). Bewitshingly, the charge transfer of Cr6+ ions, at high energy (347 nm), was explored. This, in turn, leads to a proper investigation of glass absorption edges that undergo a blue shift of about 1.25 eV. Adding 3d-transition metal ions affects crystal field splitting energy and interelectronic interaction within the d-orbitals of Cr ions. Finally, ESR data confirmed the Cr5+ state (with ESR signal at 1.92) and Cr3+ state (with ESR signal at 4.6, 4.07 and 2.04) of chromium ions. Such a cohesive investigation of the structure, optical and magnetic properties of 3d-transition metal ions-bearing chromium barium borate glass paved the route toward utilization of these samples in the optoelectronic realm.

Bistability of AlGaAs/GaAs Resonant-Tunneling Diodes Heterostructural Channel.

This paper presents an effective compact model of current transfer for the estimation of hysteresis parameters on the volt-ampere characteristics of resonant-tunneling diodes. In the framework of the compact model, the appearance of hysteresis is explained as a manifestation of internal bistability due to interelectronic interaction in the channel of the resonant-tunneling structure. Unlike the models based on the method of equivalent circuits, the interelectronic interaction in the compact model is taken into account using the concentration parameter. Model validation allowed us to confirm the high accuracy of the model not only at the initial section of the volt-ampere characteristics, but also at the hysteresis parameters traditionally predicted with low accuracy, namely the loop width (∆ < 0.5%) and contrast (∆ < 7%). Thus, it is concluded that the models are promising for integration into systems for synthesizing the electrical characteristics of resonant-tunneling diodes.

Mechanism-guided design of sulfur-modified platinum catalysts for selective hydrogenation of nitrobenzene

Sulfur modification can effectively modulate the electronic properties of the active sites on the metal catalysts and thus tune the catalytic performance. In this paper, sulfur-modified Pt/C catalysts were prepared by impregnation with a certain amount of thiourea as the precursor for the selective hydrogenation of nitrobenzene (NB) to p-aminophenol (PAP). Under reaction conditions, the highest conversion achieved was 99.5% and the selectivity was 72.5%. The effects of sulfur source type and sulfur content on the structure and physicochemical properties of catalyst support and active site were investigated. Results of XPS, H2-TPD-Mass and IR indicated the presence of strong inter-electron interaction between S and Pt. The sulfur modified catalyst not only reduces the dissociation and adsorption strength of hydrogen by Pt, but also inhibits the adsorption strength of phenylhydroxylamine on the catalyst surface, preventing excessive hydrogenation of phenylhydroxylamine, and prompting Bamberger rearrangement to p-aminophenol.

Strongly Correlated Electronic Properties of FeO Studied by the SCAN+U Functional

The recently developed strongly constrained and appropriately normed (SCAN) meta-GGA exchange-correlation functional has been demonstrated to be able to give an accurate description of strongly correlated cuprates. However, it remains to be seen if SCAN calculations can predict the physics of compounds involving partially filled 3d orbitals. In this work, we present the first-principles electronic structure studies about the phase transition of FeO using the SCAN functional. Compared with the exchange-correlation functionals widely used in density functional theory, such as the local-density approximation (LDA) or the generalized gradient approximation (GGA), SCAN correctly predicts an antiferromagnetic insulating ground state. However, it still significantly underestimates the band gap for compounds involving partially filled 3d orbitals and, hence, predicts an incorrect phase transition pressure of FeO. Interestingly, the electronic structure and band gap properties of FeO from the SCAN calculations are similar to those from the GGA+U calculations with U0 = 0.7 eV. An on-site interelectronic interaction U is therefore still needed in order to correctly describe the phase transition physics of FeO for the SCAN calculations, predominantly as a simplified self-interaction-error reduction term that enhances the spatial compactness of 3d orbitals. The required value of U in SCAN+U is less than that required in GGA+U, and their difference is rightly equal to the value of U0. Most importantly, in comparison with GGA+U, the SCAN+U method no longer needs to use the prior-known knowledge to break orbital symmetry avoiding the metastability issue, benefiting from the spontaneous symmetry breaking it allows. The calculated properties of FeO from SCAN+U agree well with experiments.

A Compact Current-Transfer Model in Resonant-Tunneling Structures with Consideration of Interelectronic Interaction

A compact analytical model of current transfer was developed to estimate the characteristics of heterostructured devices. The absence of empirical correction factors and the explicit accounting of the interelectronic interaction differentiates it from previous similar models. The model obtains an estimates of the electron density in the quantum well of the heterostructural channel and applies a self-consistent correction for resonance levels. It also provides accuracy in the positive differential resistance region of the I–V characteristics in the AlGaAs structures, with an average relative error not exceeding 2%. The time complexity of the calculations of the I–V characteristics using this model is several orders of magnitude less than that of calculations using ab initio models. Its high accuracy and low temporal complexity of calculations of I–V characteristics allow this model to be integrated in systems for the design and calculation of reliability indicators for devices, including terahertz devices.

Inter-Electronic Interaction between Ni and Mo in Electrodeposited Ni-Mo-P on 3D Copper Foam Enables Hydrogen Evolution Reaction at Low Overpotential.

Electrocatalytic hydrogen evolution reaction (HER) via water electrolysis has been considered the most effective and sustainable route to produce clean hydrogen. Designing and structure optimization are the two important parameters to develop an affordable, easy to fabricate, and stable non-noble metal electrocatalyst for the production of hydrogen as a clean, sustainable, and green fuel. Herein, we have synthesized Ni-Mo-P on copper foam (Cuf) via a facile single-step electrodeposition method, which can show stratospheric efficiency toward HER with a Tafel slope of 67 mV dec-1 and a very low overpotential of only 53 mV at a current density of 20 mA cm-2. Cuf acts as a conducting substrate support and the existence of the inter-electronic effect between Ni and Mo results in substantial catalytic activity toward hydrogen generation. In addition to this, the catalyst shows long time stability of around 97.5 h with almost negligible degradation under the applied overpotential for HER in alkaline media. This work features the significance of structure design and construction of non-noble metal catalysts via a simple method for efficient hydrogen generation.

Properties of Bound Electron Pairs

The energies of spin singlet and triplet bound electron pairs are reckoned for electrons interacting through the Coulomb interaction, while sitting on neigbouring lattice sites. It is concluded that triplet pairs are unlikely to be observed due to screening. The interplay of inter-electron couplings of different spatial range is investigated. High-pressure induced superconductivity is analysed and qualitative agreement is achieved with observed results by working out the dependence of the critical temperature on the microscopic parameters, characterising the electron motion. This approach can be applied to other kinds of inter-electron interactions.

Building machine learning assisted phase diagrams: Three chemically relevant examples

In this work, we present a systematic procedure to build phase diagrams for chemically relevant properties by the use of a semi-supervised machine learning technique called uncertainty sampling. Concretely, we focus on ground state spin multiplicity and chemical bonding properties. As a first step, we have obtained single-eutectic-point-containing solid–liquid systems that have been suitable for contrasting the validity of this approach. Once this was settled, on the one hand, we built magnetic phase diagrams for several Hooke atoms containing a few electrons (4 and 6) trapped in spheroidal harmonic potentials. Changing the parameters of the confinement potential, such as curvature and anisotropy, and interelectronic interaction strength, we have been able to obtain and rationalize magnetic phase transitions flipping the ground state spin multiplicity from singlet (nonmagnetic) to triplet (magnetic) states. On the other hand, Bader’s analysis is performed upon helium dimers confined by spherical harmonic potentials. Covalency is studied using descriptors as the sign for Δρ(rC) and H(rC), and the dependency on the degrees of freedom of the system is studied, i.e., potential curvature ω2 and interatomic distance R. As a result, we have observed that there may exist a covalent bond between He atoms for short enough distances and strong enough confinement. This machine learning procedure could, in principle, be applied to the study of other chemically relevant properties involving phase diagrams, saving a lot of computational resources.

Coupled Cluster Downfolding Theory: towards universal many-body algorithms for dimensionality reduction of composite quantum systems in chemistry and materials science

The recently introduced coupled cluster (CC) downfolding techniques for reducing the dimensionality of quantum many-body problems recast the CC formalism in the form of the renormalization procedure allowing, for the construction of effective (or downfolded) Hamiltonians in small-dimensionality sub-space, usually identified with the so-called active space, of the entire Hilbert space. The resulting downfolded Hamiltonians integrate out the external (out-of-active-space) Fermionic degrees of freedom from the internal (in-the-active-space) parameters of the wave function, which can be determined as components of the eigenvectors of the downfolded Hamiltonians in the active space. This paper will discuss the extension of non-Hermitian (associated with standard CC formulations) and Hermitian (associated with the unitary CC approaches) downfolding formulations to composite quantum systems commonly encountered in materials science and chemistry. The non-Hermitian formulation can provide a platform for developing local CC approaches, while the Hermitian one can serve as an ideal foundation for developing various quantum computing applications based on the limited quantum resources. We also discuss the algorithm for extracting the semi-analytical form of the inter-electron interactions in the active spaces.

Imaging tunable quantum Hall broken-symmetry orders in graphene.

When electrons populate a flat band their kinetic energy becomes negligible, forcing them to organize in exotic many-body states to minimize their Coulomb energy1-5. The zeroth Landau level of graphene under a magnetic field is a particularly interesting strongly interacting flat band because interelectron interactions are predicted to induce a rich variety of broken-symmetry states with distinct topological and lattice-scale orders6-11. Evidence for these states stems mostly from indirect transport experiments that suggest that broken-symmetry states are tunable by boosting the Zeeman energy12 or by dielectric screening of the Coulomb interaction13. However, confirming the existence of these ground states requires a direct visualization of their lattice-scale orders14. Here we image three distinct broken-symmetry phases in graphene using scanning tunnelling spectroscopy. We explore the phase diagram by tuning the screening of the Coulomb interaction by a low- or high-dielectric-constant environment, and with a magnetic field. In the unscreened case, we find a Kekulé bond order, consistent with observations of an insulating state undergoing a magnetic-field driven Kosterlitz-Thouless transition15,16. Under dielectric screening, a sublattice-unpolarized ground state13 emerges at low magnetic fields, and transits to a charge-density-wave order with partial sublattice polarization at higher magnetic fields. The Kekulé and charge-density-wave orders furthermore coexist with additional, secondary lattice-scale orders that enrich the phase diagram beyond current theory predictions6-10. This screening-induced tunability of broken-symmetry orders may prove valuable to uncover correlated phases of matter in other quantum materials.

Ядерное магнитное экранирование в многозарядных ионах

The nuclear magnetic shielding is considered within the fully relativistic approach for the ground state of H-, Li-, and B-like ions in the range Z=32-92. The interelectronic interaction is evaluated to the first order of the perturbation theory in Li- and B-like ions. The calculations are based on the finite-field method. The numerical solution of the Dirac equation with the magnetic-field and hyperfine interactions included within the dual-kinetic-balance method is employed. The nuclear magnetic shielding constant is an important ingredient for accurate determination of the nuclear magnetic moments from the high-precision g-factor measurements.

Effective momentum-momentum coupling in a correlated electronic system

We present a way of partly reincorporate the effects of the localized bonding electrons on the dynamics of their itinerant counterparts in Hubbard-like Hamiltonians. This is done by relaxing the constraint that the former should be entirely frozen in the chemical bonds between the underlying lattice sites through the employment of a Born-Oppenheimer-like ansatz for the wavefunction of the whole electronic system. Accordingly, the latter includes itinerant as well as bonding electron coordinates. Going beyond the adiabatic approximation, we show that the net effect of virtual transitions of bonding electrons between their ground and excited states is to furnish the itinerant electrons with an effective inter-electronic momentum-momentum interaction. Although we have applied these ideas to the specific case of rings, our assumptions can be generalized to higher dimensional systems sharing the required properties of which we have made use herein.

Symmetry-breaking polymorphous descriptions for correlated materials without interelectronic U

Correlated materials with open-shell d- and f-ions having degenerate band edge states show a rich variety of interesting properties ranging from metal-insulator transition to unconventional superconductivity. The textbook view for the electronic structure of these materials is that mean-field approaches are inappropriate, as the interelectronic interaction U is required to open a band gap between the occupied and unoccupied degenerate states while retaining symmetry. We show that the latter scenario often defining what Mott insulators are, is in fact not needed for the 3d binary oxides MnO, FeO, CoO, and NiO. The mean-field band theory can indeed lift such degeneracies in the binaries when nontrivial unit cell representations (polymorphous networks) are allowed to break symmetries, in conjunction with a recently developed non-empirical exchange and correlation density-functional without an on-site interelectronic interaction U. We explain how density-functional theory (DFT) in the polymorphous representation achieves band gap opening in correlated materials through a separate mechanism to the Mott-Hubbard approach. We show the method predicts magnetic moments and gaps for the four binary monoxides in both the antiferromagnetic and paramagnetic phases, offering an effective alternative to symmetry-conserving approaches for studying a range of functionalities in open d- and f-shell complex materials.

QED corrections to the g factor of Li- and B-like ions

QED corrections to the $g$ factor of Li-like and B-like ions in a wide range of nuclear charges are presented. Many-electron contributions as well as radiative effects on the one-loop level are calculated. Contributions resulting from the interelectronic interaction, the self-energy effect, and most of the terms of the vacuum-polarization effect are evaluated to all orders in the nuclear coupling strength $Z\alpha$. Uncertainties resulting from nuclear size effects, numerical computations, and uncalculated effects are discussed.

Electron–electron interaction energy in He-like isoelectronic sequence with Z = 2–133

Via a differential comparison of the binding energies between H- and He-like ions, the electron–electron interaction energies of the states and () in the He-like isoelectronic sequence are obtained over a wide range of the nuclear charge by using fully relativistic multiconfiguration Dirac–Hartree–Fock and configuration interaction methods. Contributions from the Coulomb and Breit interactions, the nuclear effects, the self-energy and vacuum polarization corrections are evaluated. The results show that, the one-electron corrections to the electron–electron interaction are nearly cancelled out during the deduction of the interelectron interaction energies. Besides the Coulomb interaction, the Breit interaction plays a significant role in the electron–electron interaction for high- ions; it contributes 23% of the electron–electron interaction energy at

The Dimensional Effect in the Adsorption Properties of Ultrasmall Gold Particles

In the framework of the theory of tunneling resonance electron-vibrational spectroscopy, taking into account the interelectron (Coulomb) interaction, which is essential for ultrasmall metal nanoparticles (≤5 nm), a model is constructed that quantitatively explains the results of published spectroscopic experiments carried out using scanning tunneling microscopy, in which for nanoparticles of gold (Au NPs) deposited on pyrolytic graphite, previously there were observed equidistant series of negative differential resistances with periods of 0.1–0.5 V. It was found that series with sufficiently large periods (~0.3–0.5 V), having growing (by the measure of increasing voltage on the nanocontact) envelopes correlate with the sizes of Au NPs and are formed by the Coulomb blockade mechanism. Series with small periods (~0.1 V) correspond to vibrational transitions of atomic particles adsorbed on the surface of Au NPs. A new size effect was discovered for the first time, consisting in the increased adsorption ability of ultrasmall gold nanoparticles having the same sizes (≈3.2 nm) as particles with increased catalytic activity. The new adsorption effect gives a direct and affirmative answer to the frequently discussed question of the “intrinsic” Au NP superactivity, which is not related to the properties of carriers.

Towards an Understanding of the Mode of Action of Human Aromatase Activity for Azoles through Quantum Chemical Descriptors-Based Regression and Structure Activity Relationship Modeling Analysis

Aromatase is an enzyme member of the cytochrome P450 superfamily coded by the CYP19A1 gene. Its main action is the conversion of androgens into estrogens, transforming androstenedione into estrone and testosterone into estradiol. This enzyme is present in several tissues and it has a key role in the maintenance of the balance of androgens and estrogens, and therefore in the regulation of the endocrine system. With regard to chemical safety and human health, azoles, which are used as agrochemicals and pharmaceuticals, are potential endocrine disruptors due to their agonist or antagonist interactions with the human aromatase enzyme. This theoretical study investigated the active agonist and antagonist properties of “chemical classes of azoles” to determine the relationships of azole interaction with CYP19A1, using stereochemical and electronic properties of the molecules through classification and multilinear regression (MLR) modeling. The antagonist activities for the same substituent on diazoles and triazoles vary with its chemical composition and its position and both heterocyclic systems require aromatic substituents. The triazoles require the spherical shape and diazoles have to be in proper proportion of the branching index and the number of ring systems for the inhibition. Considering the electronic aspects, triazole antagonist activity depends on the electrophilicity index that originates from interelectronic exchange interaction (ωHF) and the LUMO energy (), and the diazole antagonist activity originates from the penultimate orbital () of diazoles. The regression models for agonist activity show that it is opposed by the static charges but favored by the delocalized charges on the diazoles and thiazoles. This study proposes that the electron penetration of azoles toward heme group decides the binding behavior and stereochemistry requirement for antagonist activity against CYP19A1 enzyme.

Prediction of Free Energy by Docking Simulation using Inter-Fragment Interaction Energies

It is still difficult to predict binding free energy of novel inhibitors having potent activity in docking simulation. In recent years, the fragment molecular orbital (FMO) method has been used for the analysis of the interaction between protein and inhibitor and the sum of inter-fragment interaction energies (IFIE) between protein and inhibitor obtained by the calculation can evaluate the static interaction considering the inter-electron interaction. If there is a high correlation between IFIE and ΔH by FMO calculation, the regression between ΔH and IFIE can be constructed. Compensation law is established for ΔH and TΔS, so that finally ΔG can be predicted only IFIE. Therefore, it is possible to establish a method that can predict ΔG without considering entropy. This study examined the correlation between IFIE and ΔH of HIV protease with its inhibitors using supercomputer K and FX100. We calculated 14 complexes by the FMO calculation. The correlation between the IFIE obtained by the calculation and the experimental value was R2 = 0.3652, indicating a poor correlation. Then we analyzed the IFIE between the inhibitor and the amino acid residues. There was a difference in IFIE between inhibitor and GLY49 in each complex. From the structure, there were complexes with and without water molecules between the inhibitor and GLY49, so we classified the complex with water as group 1 and the complex without water as group 2. As a result, a better correlation of R2=0.9754 for group 1 and R2=0.7272 for group 2 was obtained. From these results, by classifying and calculated the complex according to the binding state of water, it was able to be obtained the correlation between IFIE and ΔH required for ΔG prediction.

Hall Conductivity as the Topological Invariant in the Phase Space in the Presence of Interactions and a Nonuniform Magnetic Field

The quantum Hall conductivity in the presence of constant magnetic field may be represented as the topological TKNN invariant. Recently, the generalization of this expression has been proposed for the nonuniform magnetic field. The quantum Hall conductivity is represented as the topological invariant in phase space in terms of the Wigner transformed two-point Green’s function. This representation has been derived when the interelectron interactions were neglected. It is natural to suppose, that in the presence of interactions the Hall conductivity is still given by the same expression, in which the non-interacting Green’s function is substituted by the complete two-point Green’s function including the interaction contributions. We prove this conjecture within the framework of the 2 + 1 D tight-binding model of rather general type using the ordinary perturbation theory.

Photoionization of Molecular Endohedrals

We calculate the photoionization cross-section of a molecular endohedral. We limit ourselves to two-atomic molecules. The consideration is much more complex than for atomic endohedrals because the system even for almost spherical fullerenes has only cylindrical instead of spherical symmetry. On the other hand, molecular endohedral is more interesting since the interelectron interaction in molecules is relatively stronger than in similar atoms. We present here results of calculations of molecular hydrogen stuffed inside almost spherical fullerene. For comparison, we perform calculations also for atomic endohedral with Helium inside fullerene. The results are obtained both in the single-electron Hartree-Fock approximation and with account of multi-electron correlations in the frame of so-called random phase approximation with exchange. The presence of the fullerenes shell results in prominent oscillations in the endohedrals photoionization cross section. The role of interelectron correlations becomes clear by comparing HF and RPAE results for molecular and atomic endohedral on the one side with that for corresponding isolated molecule and atom on the other.