Dipole Correction Research Articles

Hints of New Physics for the Hubble Tension: Violation of Cosmological Principle

Discrepancy between the measurements of Hubble constant H 0 from the cosmic microwave background and the local distance ladder is the most serious challenge to the standard ΛCDM model. Recent research has pointed out that it might be related with the violation of cosmological principle. Here, we investigate the impact of dipole–monopole correction on the constraints of H 0 utilizing the dipole-fitting method based on the ΛCDM model and cosmography method. Our results show that the dipole–monopole correction can reduce the constraints of H 0 from a larger value consistent with SH0ES results to a smaller value consistent with Planck results. This finding can effectively alleviate the Hubble tension. Through making redshift tomography and model-independent analyses, we confirm that our findings are independent of the redshift and cosmological model. In addition, the theoretical prediction of H(z)/(1 + z) reconstructed by the constraints of the ΛCDM model with the dipole correction is in agreement with baryon acoustic oscillation (BAO) measurements, including five Dark Energy Spectroscopic Instrument BAOs within the 1σ range except a data point at z = 0.51. Our research suggests that the Hubble tension originates from new physics beyond the standard ΛCDM model, which might lead to a violation of the cosmological principle.

Crystal structures and electronic and magnetic properties of Janus bilayer Cl[formula omitted]Cr[formula omitted]I[formula omitted]

Two-dimensional (2D) magnetic material CrI3 has aroused extensive attention, because it could provide a new platform for investigating the relations between crystal structures and electronic and magnetic properties. Here, we study crystal structures and electronic and magnetic properties of three configurations (Cl–Cl I–I and Cl–I) of Janus bilayer Cl3Cr2I3 with two stacking orders (AB and AA1/3) by using the first principles approach incorporating the spin–orbit coupling (SOC) effect and the dipole correction. It is found that the spin polarization and the SOC effect can expand the lattice constant and the interlayer distance (ID) of the three configurations. Especially, the ID of the I–I configuration is 1 Å larger than that of the Cl–Cl configuration. The total energy calculation results show that the atomic configuration, the SOC effect and the stacking order play an important role in determining the magnetic ground states of the Janus layers. Our results indicate the atomic configurations of the Janus bilayers are not conducive to the increase of critical temperature. Interestingly, the Cl–I configuration has a vertical dipole moment, and its AFM state has large spin splitting. It is revealed that the non-periodic structure, the symmetry breaking of the average potential and the weak interlayer interaction lead to the vertical dipole moment and the abnormal AFM state that is not the most stable state.

Highly stable two-dimensional Janus Transition Metal Dichalcogenide-Based van der Waals heterostructures for exceptional solar cell performance

The development and utilization of solar energy are extremely important for alleviating energy and environmental problems. Herein, we comprehensively fabricated a series of two-dimensional Janus MXY-based van der Waals heterostructures (M=Mo, W; X, Y=S, Se, Te, and X≠Y) and thoroughly investigated their potential applications in solar cells using first-principles density functional theory. Further analysis identifies 20 heterostructures with power conversion efficiencies (PCEs) exceeding 20 %. Additionally, the impact of spin-orbit coupling (SOC) effects and intrinsic dipole correction on band structures and PCEs is examined. Particularly noteworthy are the WSSe/WSeTe SeSe BB and WSeTe/WSTe TeTe BB' vdWHs, exhibiting superior PCEs of 19.25 % (23.51 %) and 21.53 % (20.49 %) with (without) SOC effects and dipole correction, alongside minimal exciton binding energies (0.36 and 0.32 eV), excellent stability, and high light absorption coefficients (105∼106 cm−1). These outstanding values surpass most reported results. These findings underscore the potential of Janus transition metal dichalcogenide (TMD) vdWHs, particularly WSSe/WSeTe SeSe BB and WSeTe/WSTe TeTe BB' configurations, for advanced solar cell applications, offering valuable theoretical insights for future experimental investigations.

Interaction Regularity of Biomolecules on Mg and Mg-Based Alloy Surfaces: A First-Principles Study

Adsorbed molecules can modulate the behavior of magnesium (Mg) and Mg alloy in biomedical applications. The interaction regularity and mechanism of biomolecules (such as amino acids, dipeptides, and tripeptide) on a Mg(0001) surface, the influence of dipole correction, and the effects of alloying elements and electronic structure were investigated in this study using first-principles calculations. Specifically, the adsorption energy (Eads) of functional groups (-NH2, -COOH and -CN3H4), amino acids (arginine (Arg), glycine (Gly), and aspartic acid (Asp)), dipeptides (arginine–glycine (Arg-Gly), glycine–aspartic acid (Gly-Asp), and arginine–aspartic acid (Arg-Asp)), and arginine–glycine–aspartic acid (RGD) tripeptide were systematically calculated. Dipole correction slightly enhanced the interaction between molecules and Mg surfaces, but the Eads trend remained unchanged. The addition of alloying elements improved the interaction of molecules and Mg-based alloy surfaces. This study will be of fundamental importance in understanding the interaction regularity of molecules on Mg and Mg-based alloy surfaces and provide possibilities for surface modification design of biomedical materials.

Role of graphene in scavenging methyl cations: a DFT study.

It is known that methylating agents methylate DNA by transferring a methyl cation (CH3+) to the nucleophilic sites in DNA bases and DNA methylation is implicated in cancer and other pathological conditions. Therefore, it is important to scavenge CH3+ ion in order to protect DNA from methylation. Graphene is considered to be a versatile material for use in a wide variety of fields including sensors, antioxidants, drug delivery and DNA sequencing. In this work, we have theoretically investigated the interaction of CH3+ ions with graphene surface with an aim to understand if pristine graphene can be used as a substrate to adsorb CH3+ cations generated from harmful methylating agents. The computed adsorption energies show that adsorption of one, two and three CH3+ ions on graphene is favourable as the adducts thus formed are found to be substantially stable in both gas phase and aqueous media. The Bader charge transfer analysis and density of states (DOS) calculation also indicate a strong interaction between graphene and CH3+ ions. Thus, our results show that pristine graphene can be used as a substrate to scavenge CH3+ ions. The spin polarised density functional theory (DFT) calculations employing PBE functional, ultrasoft pseudopotentials and plane wave basis set having kinetic energy cut-offs of 40 Ry and 400 Ry, respectively, for wave functions and charge densities were carried out to study the adsorption of CH3+ ion(s) on the pristine graphene surface. The Grimme's DFT-D2 method was used for the estimation of van der Waals interactions. The 'dipole correction' along z-direction was also applied for adsorption study. The Marzari-Vanderbilt smearing and Monkhorst-Pack k-point grid were employed for the Brillouin zone sampling. A 6 × 6 graphene supercell with a vertical cell dimension of 18Å was considered for the adsorption study. The charge transfer between the CH3+ ion(s) and graphene was estimated using Bader charge analysis. The implicit solvation model (SCCS) was used to estimate the solvent effect of aqueous media. All the calculations were performed using QUANTUM ESPRESSO package.

Ab initio vacancy formation energies and kinetics at metal surfaces under high electric field

Recording field ion microscope images under field evaporating conditions and subsequently reconstructing the underlying atomic configuration, called three-dimensional field ion microscopy (3D-FIM) is one of the few techniques capable of resolving crystalline defects at an atomic scale. However, the quantification of the observed vacancies and their origins are still a matter of debate. It was suggested that high electric fields (1-5 V/\r{A}) used in 3D-FIM could introduce artefact vacancies. To investigate such effects, we used density functional theory (DFT) simulations. Stepped Ni and Pt surfaces with kinks were modelled in the repeated slab approach with a (971) surface orientation. An electrostatic field of up to 4 V/\r{A} was introduced on one side of the slab using the generalized dipole correction. Contrary to what was proposed, we show that the formation of vacancies on the electrified metal surface is more difficult compared to a field-free case. We also find that the electric field can introduce kinetic barriers to a potential vacancy-annihilation mechanism. We rationalize these findings by comparing to insights from field evaporation models.

Boost solar-to-hydrogen efficiency by constructing heterostructures with the pristine and Se/Te-doped AgInP2S6 monolayers

To achieve high solar-to-hydrogen efficiency (η'STH), we identify the geometrical structures of seven heterostructures comprising the pristine and doped AgInP2S6 monolayers and confirm the stabilities. The electronic properties by HSE06 with dipole corrections are used to demonstrate the charge polarization and the built-in electric field in heterostructure. The direct Z-schemes for hydrogen evolution on the heterostructures are constructed based on the projected band edge potentials of each monolayer, and the corresponding s are evaluated. The results demonstrate that both doping and constructing heterostructure can significantly boost the s. Remarkably, the Se-doped AgInP2S6 monolayer promotes the from 6.41% to 12.50%, while the two configurations of the AgInP2S3Se3/AgInP2S3Te3 heterostructure raise to 17.59% and 19.88%, respectively. The corresponding total energy conversion efficiency reach 0.37% and 0.43%. Moreover, strain engineering significantly impacts with either boosting or degrading effects depending on the different strains. The highestof 31.17% can be achieved for the AgInP2S3Se3/AgInP2S3Te3 heterostructure under 4% biaxial tensile strain. The changes of −0.15–1.69 eV for the Gibbs free energies in the hydrogen evolution reactions indicate these reactions are feasible in thermodynamics. Therefore, the heterostructures based on the Se/Te doped AgInP2S6 monolayers, especially the AgInP2S3Se3/AgInP2S3Te3 one, are a potential candidate for developing high efficient photocatalysts.

Hybrid density functional theory study on zinc blende GaN and diamond surfaces and interfaces: Effects of size, hydrogen passivation, and dipole corrections

GaN-diamond heterojunctions show promise in high electron mobility transistor applications. This prompts the need for accurate models of structural and electronic properties. We detail here a hybrid density functional theory study of zinc blende (ZB) GaN and diamond heterostructures using slab supercell models. The dependence of electronic properties on supercell size, pseudo-hydrogen passivation, and dipole corrections is detailed. The larger bulk modulus of diamond is shown to provide a templating structure for GaN to grow upon, where the large lattice mismatch is accounted for through the inclusion of a cationic Ga adlayer. Looking at both type I and II surfaces and interfaces of GaN shows the instability of zb GaN without an adlayer (type II), where increased size, pseudo-hydrogen passivation and dipole corrections do not remove the spurious interaction between the top and bottom layers in type II GaN. Layer dependent density of states, local potential differences, and charge density differences show that the type I interface (with a Ga adlayer) is stable with an adhesion energy of 0.704 eV/Å2 (4.346 J/m2); interestingly, the diamond charge density intercalates into the first layer of GaN, which was seen experimentally for wurtzite GaN grown over diamond. The type II interface is shown to be unstable which implies that, to form a stable, thin-film zb interface between GaN and diamond, the partial pressure of trimethylgallium must be controlled to ensure a Ga layer exists both on the top and bottom layer of the GaN thin film atop the diamond. We believe our results lead to a better understanding of the GaN/diamond multifaceted interface present in the GaN overgrowth on diamond heterojunction used in electronic device applications.

First-principles predictions of Hall and drift mobilities in semiconductors

Significant progress on parameter-free calculations of carrier mobilities in real materials has been made during the past decade; however, the role of various approximations remains unclear and a unified methodology is lacking. Here, we present and analyse a comprehensive and efficient approach to compute the intrinsic, phonon-limited drift and Hall carrier mobilities of semiconductors, within the framework of the first-principles Boltzmann transport equation. The methodology exploits a novel approach for estimating quadrupole tensors and including them in the electron-phonon interactions, and capitalises on a rigorous and efficient procedure for numerical convergence. The accuracy reached in this work allows to assess common approximations, including the role of exchange and correlation functionals, spin-orbit coupling, pseudopotentials, Wannier interpolation, Brillouin-zone sampling, dipole and quadrupole corrections, and the relaxation-time approximation. A detailed analysis is showcased on ten prototypical semiconductors, namely diamond, silicon, GaAs, 3C-SiC, AlP, GaP, c-BN, AlAs, AlSb, and SrO. By comparing this extensive dataset with available experimental data, we explore the intrinsic nature of phonon-limited carrier transport and magnetotransport phenomena in these compounds. We find that the most accurate calculations predict Hall mobilities up to a factor of two larger than experimental data; this could point to promising experimental improvements in the samples quality, or to the limitations of density-function theory in predicting the carrier effective masses and overscreening the electron-phonon matrix elements. By setting tight standards for reliability and reproducibility, the present work aims to facilitate validation and verification of data and software towards predictive calculations of transport phenomena in semiconductors.

Critical Thermodynamic Conditions for the Formation of p-Type β-Ga2O3 with Cu Doping.

As a promising third-generation semiconductor, is facing bottleneck for its p-type doping. We investigated the electronic structures and the stability of various Cu doped structures of . We found that Cu atoms substituting Ga atoms result in p-type conductivity. We derived the temperature and absolute oxygen partial pressure dependent formation energies of various doped structures based on first principles calculation with dipole correction. Then, the critical thermodynamic condition for forming the abovementioned substitutional structure was obtained.

Constant potential simulations on a mesh.

Molecular dynamics simulations in a constant potential ensemble are an increasingly important tool to investigate charging mechanisms in next-generation energy storage devices. We present a highly efficient approach to compute electrostatic interactions in simulations employing a constant potential method (CPM) by introducing a particle-particle particle-mesh solver specifically designed for treating long-range interactions in a CPM. Moreover, we present evidence that a dipole correction term-commonly used in simulations with a slab-like geometry-must be used with caution if it is also to be used within a CPM. It is demonstrated that artifacts arising from the usage of the dipole correction term can be circumvented by enforcing a charge neutrality condition in the evaluation of the electrode charges at a given external potential.

Electromagnetic response of composite Dirac fermions in the half-filled Landau level

An effective field theory of composite Dirac fermions was proposed by Son [Phys. Rev. X 5, 031027 (2015)] as a theory of the half-filled Landau level with explicit particle-hole symmetry. We compute the electromagnetic response of this Son-Dirac theory on the level of the random phase approximation (RPA), where we pay particular attention to the effect of an additional composite-fermion dipole term that is needed to restore Galilean invariance. We find that once this dipole correction is taken into account, spurious interband transitions and collective modes that are present in the response of the unmodified theory either cancel or are strongly suppressed. We demonstrate that this gives rise to a consistent theory of the half-filled Landau level valid at all frequencies, at least to leading order in the momentum. In addition, the dipole contribution modifies the Fermi-liquid response at small frequency and momentum, which is a prediction of the Son-Dirac theory within the RPA that distinguishes it from a separate description of the half-filled Landau level by Halperin, Lee, and Read within the RPA.

An Efficient Method for Determining Matrix Elements of the Dipole Moment Operator and Corrections to the Energy of a Polyatomic Molecule Using the Perturbation Theory within the Polynomials of Quantum Numbers Formalism

An Efficient Method for Determining Matrix Elements of the Dipole Moment Operator and Corrections to the Energy of a Polyatomic Molecule Using the Perturbation Theory within the Polynomials of Quantum Numbers Formalism

First-Principles Study of Graphene-6H SiC Surface Interactions

Interactions of graphene with 6H-SiC {0001} surfaces are numerically investigated from first principles. In order to describe the bulk structure and its 6 bilayer thick surfaces correctly, bare and dipole-corrected atomic relaxations are considered. The obtained lattice parameters and bulk modulus are in good agreement with experimental values. The calculated indirect band gap width of 2.10 eV is smaller than the experimental value due to the nature of the computational method. Geometrical optimization of the surfaces, where dipole correction is applied, reveals that the first two bilayers displace significantly, where the relaxations of the very top bilayer is more pronounced. Band structures of the {0001} surfaces possess two flat bands around the Fermi level due to unsaturated bonds on opposite faces. When one layer of C atoms are introduced on the Si-terminated surface, it behaves as a tightly-bound buffer layer. This is also the case for the C-terminated surface when van der Waals interactions are taken into account. In contrast, disregarding these interactions yields free-standing graphene like behavior for the first C overlayer. On both surfaces, the second C overlayer is free-standing where the corresponding band structures incorporate Dirac-cone like features.

Probing the universality of acceleration scale in modified Newtonian dynamics with SPARC galaxies * *Supported by the National Natural Science Fund of China (11603005, 11775038, 11947406), Fundamental Research Funds for the Central Universities (2020CQJQY-Z003)

We probe the universality of acceleration scale in Milgrom's modified Newtonian dynamics (MOND) using the recently released rotation curve data from SPARC galaxies. We divide the SPARC data into different subsamples according to the morphological types of galaxies, and fit the rotation curve data of each subsample with the theoretical prediction of MOND. MOND involves an arbitrary interpolation function which connects the Newtonian region and the MOND region. Here we consider five different interpolation functions that are widely discussed in the literature. It is shown that the best-fitting significantly depends on the interpolation functions. For a specific interpolation function, also depends on the morphological types of galaxies, implying that may be not a universal constant. Introducing a dipole correction to can significantly improve the fits. The dipole directions for four of the five interpolation functions point towards an approximately consistent direction, but still varies for different interpolation functions.

Hybrid functional investigation of band offsets for non-polar, Ga-polar and Al-polar interfaces in GaN/AlN heterojunction

We investigated band alignment of non-polar and polar GaN/AlN heterojunction by using density functional theory with the Heyd–Scuseria–Ernzerhof hybrid functional. In the heterojunction model, AlN was considered as a substrate while strained GaN was grown on top. The deformation potential of GaN, were included to calculate the unstrained band offsets. For polar heterojunction, the artificial effects from an undesired interface was removed by using vacuum insertion and dipole correction. We found that the unstrained valence band offsets (VBOs) are 0.92 eV, 1.23 eV and 1.09 eV for non-polar, Ga-polar and Al-polar interfaces respectively. The variation of VBOs can be explained from the difference in both deformation and dipole potential at the interfaces. Moreover, the additional energy shift of polar VBO from non-polar VBO were extracted as 0.33 eV from considering the effect of spontaneous polarization.

Predicting the Catalytic Activity of Surface Oxidation Reactions by Ionization Energies

Developing a descriptor to understand the reactivity of a catalyst is critical in achieving the rational design of heterogeneous catalysts. Ideally, the descriptor should be simple, predictive, as ...

Engineering Electronic Structure of Single-Atom Pd Site on Ti 0.87 O 2 Nanosheet via Charge Transfer Enables C–Br Cleavage for Room-Temperature Suzuki Coupling

The palladium (Pd)-catalyzed Suzuki reaction is widely applied in the pharmaceutical industry, where constructing highly active and low-cost Pd sites are impendent. Here, we report the fabrication ...

Perspectives of perihelion precession in torsion modified gravity

Killing symmetries are revisited in [Formula: see text] bulk geometric torsion (GT) perturbation theory to investigate the perihelion precession. Computation reveals a nonperturbative (NP) modification to the precession known in General Relativity (GR). Remarkably the analysis reassures our proposed holographic correspondence between a perturbative GT in bulk and a boundary GR coupled to [Formula: see text]. In fact, the topological correction is sourced by a non-Newtonian potential in GR and we identify it with an “electro-gravito” (EG) dipole. Interestingly, the dipole correction is shown to possess its origin in a [Formula: see text]-form underlying a propagating GT and leads to a NP gravity in [Formula: see text].

Generalized dipole correction for charged surfaces in the repeated-slab approach

First-principles calculations of surfaces or two-dimensional materials with a finite surface charge invariably include an implicit or explicit compensating countercharge. We show that an ideal constant-charge counterelectrode in the vacuum region can be introduced by means of a simple correction to the electrostatic potential in close analogy to the well-known dipole correction for charge-neutral asymmetric slabs. Our generalized dipole correction accounts simultaneously for the sheet-charge electrode and the huge voltage built up between the system of interest and the counterelectrode. We demonstrate its usefulness for two prototypical cases, namely, field evaporation in the presence of huge electric fields (20 V/nm) and the modeling of charged defects at an insulator surface. We also introduce algorithmic improvements to charge initialization and preconditioning in the density functional theory algorithm that proved crucial for ensuring rapid convergence in slab systems with high electric fields.