Coulomb Corrections Research Articles

First-principales study of the structural, magnetic and optoelectronic properties of double perovskite Ba2FeReO6

In this study, we investigate the electronic, magnetic, and optical properties of the Ba2FeReO6 double perovskite using density functional theory within the framework of the full-potential linearized augmented plane Wave method. We employ various approximations including GGA-PBE, GGA + U (Hubbard Coulomb correction), and GGA plus Spin-Orbit coupling (GGA + SOC). The densities of states and spin-polarized band structure reveal a half-metallic behavior with a magnetic moment of 3 μ B for all approximations, with iron and rhenium atoms contributing the most to the overall magnetic moment. Regarding optical properties, it can be stated that the Ba2FeReO6 material exhibits strong absorption and holds potential for application across a wide energy range spanning from visible to ultraviolet light spectra in future spintronics and optoelectronic technologies.

All orders factorization and the Coulomb problem

In the limit of large nuclear charge, Z≫1, or small lepton velocity, β≪1, Coulomb corrections to nuclear beta decay and related processes are enhanced as Zα/β and become large or even nonperturbative (with α the QED fine structure constant). We provide a constructive demonstration of factorization to all orders in perturbation theory for these processes and compute the all-orders hard and soft functions appearing in the factorization formula. We clarify the relationship between effective field theory amplitudes and historical treatments of beta decay in terms of a Fermi function. Published by the American Physical Society 2024

LibMBD: A general-purpose package for scalable quantum many-body dispersion calculations.

Many-body dispersion (MBD) is a powerful framework to treat van der Waals (vdW) dispersion interactions in density-functional theory and related atomistic modeling methods. Several independent implementations of MBD with varying degree of functionality exist across a number of electronic structure codes, which both limits the current users of those codes and complicates dissemination of new variants of MBD. Here, we develop and document libMBD, a library implementation of MBD that is functionally complete, efficient, easy to integrate with any electronic structure code, and already integrated in FHI-aims, DFTB+, VASP, Q-Chem, CASTEP, and Quantum ESPRESSO. libMBD is written in modern Fortran with bindings to C and Python, uses MPI/ScaLAPACK for parallelization, and implements MBD for both finite and periodic systems, with analytical gradients with respect to all input parameters. The computational cost has asymptotic cubic scaling with system size, and evaluation of gradients only changes the prefactor of the scaling law, with libMBD exhibiting strong scaling up to 256 processor cores. Other MBD properties beyond energy and gradients can be calculated with libMBD, such as the charge-density polarization, first-order Coulomb correction, the dielectric function, or the order-by-order expansion of the energy in the dipole interaction. Calculations on supramolecular complexes with MBD-corrected electronic structure methods and a meta-review of previous applications of MBD demonstrate the broad applicability of the libMBD package to treat vdW interactions.

Electronic structure of SrFe1−x(Mn,Co)xO3-δ: A CPA case study

A new methodology is suggested for determining and using the Coulomb interaction parameter U(t2g), taking into account the different energy localizations of t2g and eg states in disordered transition metal perovskite-like oxides, based on the local spin density approximation with Coulomb interaction correction method and the coherent potential approximation. The adjustment of U(t2g)’s relies on the best coincidence of the experimental and calculated maxima in X-ray absorption/reflection spectra at simultaneous demand for the calculated magnetic moments to closely correspond to their experimental values in cubic oxides SrFeO3, SrMnO3, and SrCoO3. Then, the obtained U’s are utilized in order to construct the Green functions for calculating the electronic properties of strongly correlated perovskite-like solid solutions within the coherent potential method. The high efficiency of the proposed methodology has been demonstrated by a close coincidence of the experimentally observed and calculated X-ray emission/absorption spectra, magnetic moments, density of states at the Fermi level, and electronic conductivity in the disordered non-stoichiometric SrFeO3-δ, SrFe0.75Mn0.25O3-δ, and SrFe0.85Co0.15O3-δ phases. The composition SrFe0.85Co0.15O3-δ is proposed as a promising electrode material with enhanced characteristics of electric transport.

Doubly Screened Coulomb Correction Approach for Strongly Correlated Systems.

Strongly correlated systems containing d/f electrons present a challenge to conventional density functional theory such as the local density approximation or generalized gradient approximation. We developed a doubly screened Coulomb correction (DSCC) approach to perform on-site Coulomb interaction correction for strongly correlated materials. The on-site Coulomb interaction between localized d/f electrons is self-consistently determined from a model dielectric function that includes both the static dielectric and Thomas-Fermi screening. We applied DSCC to simulate the electronic and magnetic properties of typical 3d, 4f, and 5f strongly correlated systems. The accuracy of DSCC is comparable to that of hybrid functionals but an order of magnitude faster. In addition, DSCC can reflect the difference in the Coulomb interaction between metallic and insulating situations, similar to the popular but computationally expensive constrained random phase approximation approach. This feature suggests that DSCC is also a promising method for simulating Coulomb interaction parameters.

All-Order Coulomb Corrections to Delbrück Scattering above the Pair-Production Threshold.

We report calculations of Delbrück scattering that include all-order Coulomb corrections for photon energies above the threshold of electron-positron pair creation. Our approach is based on the application of the Dirac-Coulomb Green's function and accounts for the interaction between the virtual electron-positron pair and the nucleus to all orders in the nuclear binding strength parameter αZ. Practical calculations are performed for the scattering of 2.754MeV photons off plutonium atoms. We find that including the Coulomb corrections enhances the scattering cross section by up to 50% in this case. The obtained results resolve the long-standing discrepancy between experimental data and theoretical predictions and demonstrate that an accurate treatment of the Coulomb corrections is crucial for the interpretation of existing and guidance of future Delbrück scattering experiments on heavy atoms.

Coulomb Corrections for Bose–Einstein Correlations from One- and Three-Dimensional Lévy-Type Source Functions

In the study of femtoscopic correlations in high-energy physics, besides Bose–Einstein correlations, one has to take final-state interactions into account. Amongst them, Coulomb interactions play a prominent role in the case of charged particles. Recent measurements have shown that in heavy-ion collisions, Bose–Einstein correlations can be best described by Lévy-type sources instead of the more common Gaussian assumption. Furthermore, three-dimensional measurements have indicated that, depending on the choice of frame, a deviation from spherical symmetry observed under the assumption of Gaussian source functions persists in the case of Lévy-type sources. To clarify such three-dimensional Lévy-type correlation measurements, it is thus important to study the effect of Coulomb interactions in the case of non-spherical Lévy sources. We calculated the Coulomb correction factor numerically in the case of such a source function for assorted kinematic domains and parameter values using the Metropolis–Hastings algorithm and compared our results with previous methods to treat Coulomb interactions in the presence of Lévy sources.

Coulomb corrected nonadiabatic instantaneous ionization rate and the electron trajectory in an elliptically polarized laser field

This paper presents an analytical model that investigates the impact of Coulomb effect on tunneling ionization events in an elliptically polarized laser field. The model focuses on ionization rate and momenta, at a specific moment, based on recent experimental findings and strong-field approximation. Results show that incorporating Coulomb correction improves photoionization rate across various intensities and provides valuable insights into ionization mechanism, particularly for argon atoms at 410 and 800 nm wavelengths. This has significant implications for attosecond physics and ultrafast laser technology.

Hubbard Model Calculations for Zinc Oxide Semiconductor

To investigate the effects of Hubbard on-site Coulombic correction on the structural and electronical characteristics of wurtzite zinc oxide, first-principles calculations using density functional theory (DFT) were carried out. Because of the changes in structural characteristics brought about by the correction of hybridization between Zn 3d and O 2p states, suitable Hubbard terms need to be constructed before one can make an accurate forecast of the properties of ZnO. The computations were carried out by applying Hubbard corrections Ud to Zn 3d states and Up to O 2p states. These adjustments were based on the Wu-Cohen functional. When the Hubbard corrections Ud and Up were introduced to the calculation, the lattice parameters were more comparable to the experimental data and were found to be accurately predicted. The combination of the correction terms Ud and Up was successful in improving the underestimated bandgap of the wurtzite ZnO, which may have solved the difficulties that are associated with the traditional DFT. There is a strong agreement between the experimental bandgap and the best Hubbard parameters that were discovered for GGA-WC+U. These parameters were found to be Ud = 8 eV and Up = 8 eV.

Using analytically-corrected semiclassical rescattering model to study Coulomb impact in spiderlike photoelectron momentum distributions

We present a numerical investigation on the impact of the Coulomb interaction in the spiderlike photoelectron momentum distributions (PMDs) of a hydrogen atom ionized by an intense laser pulse. We have shown, by integrating analytical correction terms into the standard semiclassical rescattering model (SRM) to formulate the Coulomb analytically-corrected SRM (AC-SRM), that the interference fringes manifest a systematic shift along the transverse momentum direction upon considering the Coulomb action. A Coulomb correction to the SRM model has rarely been reported before. Analyses are made by varying physical quantities such as the carrier frequency and initial transverse velocity of the ionized electron. In particular, we decipher the impact of the Coulomb interaction with the classical-action phase map scheme, and demonstrate that this effect is more pronounced for smaller momenta in the spiderlike PMDs. It is proven that the presented AC-SRM is simple and effective in accounting for the Coulomb effect, as an alternative correction due to the Coulomb interaction to the standard SRM theory. Also, our phase map scheme is shown to be more powerful than the plain interference fringes in interrogating the Coulomb effect, especially for the first interference minimum. We anticipate that the present AC-SRM can be useful in investigating other strong field processes where the Coulomb interaction is considered.

Polarons: Energetics and their structural and electronic effects in ATiO3 perovskite systems

Understanding the formation of a polaron near vacancies in oxides is of vital importance for controlling defect properties and related functionalities. We examine the energetics and local structure of polarons in the vicinity of oxygen vacancies using density functional theory with the Hubbard on-site Coulombic correction. We systematically consider several $\mathrm{ATi}{\mathrm{O}}_{3}$ perovskite systems: cubic $\mathrm{SrTi}{\mathrm{O}}_{3}$ (c-STO), cubic $\mathrm{BaTi}{\mathrm{O}}_{3}$ (c-BTO), cubic $\mathrm{PbTi}{\mathrm{O}}_{3}$ (c-PTO), tetragonal $\mathrm{BaTi}{\mathrm{O}}_{3}$ (t-BTO), and tetragonal $\mathrm{PbTi}{\mathrm{O}}_{3}$ (t-PTO). The polaron formation energies vary by several orders of magnitude across the systems, where PTO systems have large polaron formation energies $(\ensuremath{\sim}\ensuremath{-}1.688\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$, c-BTO is intermediate (\ensuremath{-}0.234 eV), and c-STO and t-BTO have considerably smaller formation energies $(<\ensuremath{-}0.01\phantom{\rule{0.16em}{0ex}}\mathrm{eV})$. The formation of a polaron is found to influence the charge density, atomic displacement, and electronic structure, with higher polaron energies corresponding to larger charge density changes and greater displacements of the ions surrounding the oxygen vacancy, especially the displacement of the first nearest neighbor A-site. Finally, a comparison of the projected band structures shows fictitious in-gap states present in the delocalized picture of the system moving to the conduction and valence bands in the polaron solution of the system, indicating an incompleteness of the description of a vacancy without considering charge localization as in the polaron picture. In this paper, we provide fundamental properties of polarons near vacancies, which can be used to control and tune defect, charge transport, magnetoelectric, and multiferroic properties of perovskite oxides.

Relativistic strong-field ionization of hydrogenlike atomic systems in constant crossed electromagnetic fields

Relativistic strong-field ionization of hydrogen-like atoms or ions in a constant crossed electromagnetic field is studied. The transition amplitude is formulated within the strong-field approximation in G\"oppert-Mayer gauge, with initial and final electron states being described by the corresponding Dirac-Coulomb and Dirac-Volkov wave functions, respectively. Coulomb corrections to the electron motion during tunneling are taken into account by adjusting an established method to the present situation. Total and energy-differential ionization rates are calculated and compared with predictions from other theories in a wide range of atomic numbers and applied field strengths.

Comparative study of first-principles approaches for effective Coulomb interaction strength Ueff between localized f-electrons: Lanthanide metals as an example.

As correlation strength has a key influence on the simulation of strongly correlated materials, many approaches have been proposed to obtain the parameter using first-principles calculations. However, a comparison of the different Coulomb strengths obtained using these approaches and an investigation of the mechanisms behind them are still needed. Taking lanthanide metals as an example, we research the factors that affect the effective Coulomb interaction strength, Ueff, by local screened Coulomb correction (LSCC), linear response (LR), and constrained random-phase approximation (cRPA) in the Vienna Ab initio Simulation Package. The Ueff LSCC value increases from 4.75 to 7.78eV, Ueff LR is almost stable at about 6.0eV (except for Eu, Er, and Yb), and Ueff cRPA shows a two-stage decreasing trend in both light and heavy lanthanides. To investigate these differences, we establish a scheme to analyze the coexistence and competition between the orbital localization and the screening effect. We find that LSCC and cRPA are dominated by the orbital localization and the screening effect, respectively, whereas LR shows the balance of the competition between the two factors. Additionally, the performance of these approaches is influenced by different starting points from the Perdew-Burke-Ernzerhof (PBE) and PBE + U, especially for cRPA. Our results provide useful knowledge for understanding the Ueff of lanthanide materials, and similar analyses can also be used in the research of other correlation strength simulation approaches.

Charge asymmetry in the spectra of bremsstrahlung and pair production

We calculate the first Coulomb correction to the spectra of two processes: the electron bremsstrahlung and electron-positron photoproduction in the Coulomb field. We show that, in contrast to the results obtained in the Born approximation and in the high-energy limit, the obtained corrections for these two process are not related by the crossing symmetry substitutions. The found corrections determine the leading contribution to the charge asymmetry in these processes. We use modern multiloop methods based on the IBP reduction and on the differential equations for master integrals. The results are presented in terms of classical polylogarithms. We provide both the threshold and the high-energy asymptotics of the obtained expressions and compare them with available results.

Fabrication of supported Pt/CeO2 nanocatalysts doped with different elements for CO oxidation: theoretical and experimental studies.

Supported Pt/CeO2 catalysts have been widely used in carbon monoxide (CO) oxidation; however, the high oxygen vacancy formation energy (Evac) in the process leads to the poor performance of these catalysts. Herein, we explored different element (Pr, Cu, or N) doped CeO2 supports using Ce-based metal-organic frameworks (MOFs) as precursors via calcination treatment. The obtained CeO2 supports were used to load Pt nanoparticles. These catalysts were systematically characterized by various techniques, and they showed superior catalytic activity for CO oxidation compared to undoped catalysts which could be attributed to the formation of Ce3+, and high amounts of Oads/(Oads + Olat) and Ptδ+/Pttotal. Moreover, density functional theory calculations with on-site Coulomb interaction correction (DFT+U) were performed to provide atomic-scale insights into the reaction process by the Mars-van Krevelen (M-vK) mechanism, which revealed that the element-doped catalysts could simultaneously reduce the adsorption energies of CO and lower reaction energy barriers in the *OOCO associative pathway.

Isospin symmetry breaking in the charge radius difference of mirror nuclei

Isospin symmetry breaking (ISB) effects in the charge radius difference $\mathrm{\ensuremath{\Delta}}{R}_{\mathrm{ch}}$ of mirror nuclei are studied using the test example of $^{48}\mathrm{Ca}$ and $^{48}\mathrm{Ni}$. This choice allows for a transparent study of ISB contributions since pairing and deformation effects, commonly required for the study of mirror nuclei, can be neglected in this specific pair. The connection of $\mathrm{\ensuremath{\Delta}}{R}_{\mathrm{ch}}$ with the nuclear equation of state and the effect of ISB on such a relation are discussed according to an energy density functional approach. We find that nuclear ISB effects may shift the estimated value for the symmetry energy slope parameter $L$ by about 6 to 14 MeV while Coulomb corrections can be neglected. ISB effects on the ground-state energy and charge radii in mirror nuclei have been recently predicted by ab initio calculations to be relatively small, pointing to a negligible effect for the extraction of information on the nuclear EoS. These contrasting results call for a dedicated theoretical effort to solve this overarching problem that impacts not only the neutron-skin thickness or the difference in mass and charge radii of mirror nuclei but also other observables such as the isobaric analog state energy.

Charge-orbital Ordering, Magnetic State, and Exchange Couplings in Quasi-One-Dimensional Vanadate V6O13

Charge and orbital ordering, magnetic state, and exchange couplings in quasi-one-dimensional vanadate V6O13, a potential cathode material for Li-ion batteries, are investigated using the density functional theory with Coulomb interaction correction method (DFT + U). While the difference between {{t}_{{2g}}} orbital occupancies of V4+ (with a nominal 3{{d}^{1}} electronic configuration) and V5+ ions is large and gives direct evidence for charge and orbital ordering, the screening is so effective that the total 3d charge disproportionation is rather small. Our results show that the occupied {{t}_{{2g}}} states of V4+ ions in the single V–V layer form a spin-singlet molecular orbital, while the rest half of V4+ ions in the structurally distinct double V–V layers order antiferromagnetically in the low-temperature insulating phase of V6O13. We conclude that the metal-insulator transition and low-temperature magnetic properties of V6O13 involve the spin-Peierls transition assisted by orbital ordering and concomitant distortions of the crystal structure.

Impact of Anionic Substitution in Yb14MgSb11-x As x Compounds on the Electronic and Thermoelectric Properties.

The effects of anionic site substitution on the electronic transport properties of Yb14MgSb11-x As x compounds were investigated using density functional theory (DFT) with on-site Coulomb interaction correction (PBE+U). By replacing the Sb atoms at the four symmetry sites in Yb14MgSb11 with As, we found that the electronic and thermoelectric properties of the compound can be altered substantially. For most of the cases, the thermoelectric properties improve compared to the base compound Yb14MgSb11. Substitution at the tetrahedral site (Sb2) in particular yields the highest improvement in the thermoelectric properties. Detailed insight into the electronic and structural changes caused by the selective site substitutions is also discussed.

Complete Coulomb correction to the Molière screening angle

Nonperturbative (Coulomb) correction to the Molière screening angle in the multiple Coulomb scattering theory is evaluated taking into account the inelastic contribution. Treating the atom as an assembly of pointlike electrons and the nucleus, and summing the scattering probability over all the final states of the atom, it is shown that besides the Coulomb correction due to close encounters of the incident charged particle with atomic nuclei, there are similar corrections due to close encounters with atomic electrons, being the counterpart of Bloch correction in ionization energy loss. For low Zne 1 the latter contribution can reach sim 25%.

The structural, elastic, electronic, magnetic and optical properties of SrNiO3 perovskite: A DFT and DFT+U study

Transition-metal based half-metallic oxide perovskites are the phenomenal prospect of spintronics for their expectancy of success in information technology. Generalized gradient approximation (GGA) with Perdew–Burke–Ernzerhof (PBE) functional and also adding on-site Coulomb interaction correction (GGA-PBE+U) is implemented within density functional theory (DFT) to analyze the structural, elastic, electronic, magnetic, and optical properties of the oxide perovskites SrNiO3. The structural properties such as lattice parameter, cell volume, total energy, bulk modulus, and pressure derivative are computed at zero pressure. The elastic constants corroborate the material’s mechanical stability and stiffness. The Cauchy pressure, bulk/shear ratio, and Poisson’s ratio values indicate that this material is ductile. The electronic properties, including band structures, total and partial density of states, especially hybridization among Ni 3d and O 2p orbitals, result in half-metallic ferromagnetism. The magnetic moment of the Ni atom keeps rising gradually as the U value increases. Electronic structures are used to analyze and explain the real and imaginary parts of the dielectric function, absorption coefficient, energy loss function, reflectivity, refractive index, and extinction coefficient. Our findings suggest that this compound could be an excellent fit for spintronics applications.