Atomic Calculations Research Articles

Creation, annihilation and transport of nonmagnetic antiskyrmions within Ginzburg–Landau–Devonshire model

Atomistic model calculations recently revealed that the polarization pattern at the cross section through nanoscale ferroelectric nanodomains in rhombohedral barium titanate shows a clear antiskyrmion attributes such as the net invariant topological charge of minus two. The present work confirms that these topological defects also exist as local minima in the discretized Ginzburg–Landau–Devonshire model, which is widely used in phase-field modeling studies. We explore by phase-field simulations how an electric field can be used to create or move antiskyrmions within a monodomain ferroelectric matrix. The process of field-induced antiskyrmion annihilation reveals the existence of a discrete ladder of intermediate antiskyrmion states with distinct radii but common symmetry, topology, and geometrical properties.

Strong atomic reconstruction in twisted bilayers of highly flexible InSe: Machine-learned interatomic potential and continuum model approaches

The relaxation of atomic positions to their optimal structural arrangement is crucial for understanding the emergence of new physical behavior in long scale superstructures in twisted bilayers of two-dimensional materials. The amount of deviation from a rigid moiré structure will depend on the elastic properties of the constituent monolayers which, for the twisted bilayer, the more flexible the monolayers are, the lower the energy required to deform the layers to maximize the areas with an energetically optimal interlayer arrangement of atoms. We investigate this atomic reconstruction for twisted bilayers of highly flexible InSe. Results using two methods are demonstrated: first we train a machine-learned interatomic potential (MLIP) to enable fully atomistic relaxations of small-twist-angle large-length-scale moiré supercells while retaining density functional theory (DFT) level accuracy. We find substantial out-of-plane corrugation and in-plane domain formation for a wide range of twist angles and moiré length scales. We then adapt an existing continuum approach and show that it can reproduce some, but not all, features of the fully atomistic calculations. Published by the American Physical Society 2025

Discovery of Isograndidentatin D, a Novel Phenolic Glycoside, and Anti-Helicobacter pylori Phenolics from Salix koreensis Twigs.

Salix koreensis Anderss (Salicaceae), commonly referred to as Korean willow, is native to East Asia, particularly Korea and China, and it has been used in traditional Korean folk medicine for its potent anti-inflammatory, analgesic, and antioxidant properties. In our ongoing research efforts to discover biologically new natural products, phytochemical analysis on an ethanolic extract of S. koreensis twigs yielded the isolation and identification of ten phenolic compounds (1-10), including a newly discovered phenolic glycoside (1) named isograndidentatin D, isolated via HPLC purification. The structure of compound 1 was determined through extensive 1D and 2D NMR spectral data analysis and high-resolution electrospray ionization mass spectrometry (HR-ESIMS). Its absolute configuration was established using DP4+ probability analysis combined with gauge-including atomic orbital NMR chemical shift calculations and chemical reaction methods. The other known compounds were identified as isograndidentatin B (2), trichocarposide (3), glanduloidin C (4), tremuloidin (5), 3-O-acetylsalicin (6), 2-O-acetylsalicin (7), salicin (8), salireposide (9), and coumaric acid (10), confirmed by comparing their NMR spectra with previously reported data and further verified through liquid chromatography/mass spectrometry (LC/MS) analysis. The isolated compounds 1-10 were tested for their anti-Helicobacter pylori activities. Among these, compounds 4 and 5 demonstrated moderate anti-H. pylori activity at a concentration of 100 μM. Specifically, compound 5 showed an inhibitory activity of 35.9 ± 5.4%, making it slightly more potent than compound 4, with 34.0 ± 1.0% inhibition. These results were comparable to that of quercetin, a known anti-H. pylori agent used as a positive control in this study, which showed 38.4 ± 2.3% inhibition. The remaining compounds exhibited very weak inhibitory effects. This study highlights the potential of S. koreensis twigs as a valuable natural source of bioactive compounds for therapeutic applications against H. pylori.

Elastic limit and relaxation of GaAs/In(Al,Ga)As core/shell nanowires for near-infrared applications

In the GaAs/Inx(Al,Ga)1-xAs core/shell nanowire (CSNW) geometry, narrow cores exhibit significant bandgap reduction and enhanced electron mobility because of their ability to sustain extreme tensile elastic strain. In such an elastic state, the coherency limits and the resulting physical properties of the nanowires are governed by the strain field distribution and plastic relaxation mechanisms. Using atomic-resolution transmission electron microscopy, we determined the three-dimensional strain field, critical misfit, and plastic relaxation relative to the indium content of the shell, while maintaining constant core-shell dimensions. The strain was mapped experimentally in both coherent and plastically relaxed nanowires with a core radius of 10 nm and thick shells and was compared to atomistic and continuum calculations. Our findings reveal that, while axial strains remain uniform, elastic relaxation induces radial and tangential strain gradients. This is attributed to the strain concentration at the sharp interfaces, which persisted even after plastic relaxation. For the pertinent growth conditions, the maximum sustained elastic strain in the cores was observed for the GaAs/In0.5Al0.5As nanowires. The plastic relaxation of nanowires with shells of high indium content involved Frank partials delimiting horizontal intrinsic stacking faults (SFs), misfit dislocations gliding on inclined close-packed planes, and stair-rod dislocations along SF junction lines attributed to nanowire bending.Ab initiocalculations showed that the heterojunction remained type I even for the highest elastic strain, despite the existence of strain gradients at the core-shell interface. Our results elucidate the elastoplastic behaviour of CSNWs with narrow cores, offering new perspectives on growth strategies to further push their coherency limits.

Atomic level insight into the variation and tunability of band alignment between Si and amorphous SiO2/HfO2

Abstract The band alignment between silicon and high-k dielectric, which is a key factor to device operation and device reliability, is still suffering from uncontrolled fluctuation and ambiguous understanding. Here by conducting atomic level ab initio calculations on realistic Si/SiO2/HfO2 stacks, we manage to reveal the physical origin of band alignment fluctuations, i.e. oxygen density dependent interface and surface dipoles, and demonstrate that the band offsets can be tuned without introducing other materials. This is instructive to reduce gate tunneling current, alleviate device-to-device variation, and tune threshold voltage. Besides, this study indicates that great attention should be paid to model construction in the emerging atomistic study of semiconductor devices.

UNTANGLING THE VALLEY STRUCTURE OF STATES FOR INTRAVALLEY EXCHANGE ANISOTROPY IN LEAD CHALCOGENIDES QUANTUM DOTS

We put forward a generalized procedure which allows to restore the bulk-like electron and hole wave functions localized in certain valleys from the wave functions of quantum confined electron/hole states obtained in atomistic calculations of nanostructures. The procedure is applied to the lead chalcogenide quantum dots to accurately extract the intravalley velocity matrix elements and the constants of the effective intravalley Hamiltonian of the exchange interaction for the ground exciton state in PbS and PbSe quantum dots. Our results suggest that intravalley parameters in PbS quantum dots are much more anisotropic than the ones in PbSe. Renormalization of the velocity matrix elements, forbidden band gap, valley and exchange splittings of exciton and exciton binding energy are also calculated.

A real-time deep learning model to narrow the gap between atomic scanning transmission electron microscopy and theory calculations: Recognition, reconstruction, and simulation

A real-time deep learning model to narrow the gap between atomic scanning transmission electron microscopy and theory calculations: Recognition, reconstruction, and simulation

B-Spline Solution of the Two-Center Dirac Equation in the Electronic Continuum for Relativistic Molecular Photoionization.

In this work, the two-center Dirac equation is solved numerically using an extension of an adapted B-spline basis set method previously implemented in relativistic atomic calculations (Fischer, C. F.; Zatsarinny, O. Comput. Phys. Commun. 2009, 180, 879). The robustness of the chosen numerical method, which avoids the appearance of spurious states common in other approaches, allows us to investigate molecular photoionization within a relativistic framework by simply adapting those methods already available in the nonrelativistic case (Brosolo, M.; Decleva, P. Chem. Phys. 1992, 159, 185; Brosolo, M.; Decleva, P.; Lisini, A. Mol. Opt. Phys. 1992, 25, 3345). First, light diatomic molecules (i.e., H2+ and HeH2+) are investigated with the purpose of testing the validity and efficiency of the method. Then, a series of one-electron molecular hydrides (i.e., HF9+, HCl17+ and HI53+) is explored by computing the total photoionization cross sections, asymmetry β-parameters and partial phase shifts. The present methodology can be easily extended to treat N-electron molecules following previous approaches in nonrelativistic calculations (Plesiat, E.; Decleva, P.; Martin, F. Phys. Chem. Chem. Phys. 2012, 14, 10853). The inclusion of a second photon can be also accomplished just like in atomic investigations aiming at reproducing pump-probe experiments capable to extract the photoionization time-delays (Vinbladh, J.; Dahlstrom, J. M.; Lindroth, E. Phys. Rev A 2019, 100, 043424; Vinblach, J.; Dahlstrom, J. M.; Lindroth, E. Atoms 2022, 10, 80).

Synthesizing ordered polar patterns in nonpolar SrTiO3 nanofilms via wrinkle-induced flexoelectricity

Ordered polar structures in oxide nanofilms play a pivotal role in the development of nanoelectronic applications. Hitherto, ordered polar structures have been restricted to a limited number of ferroelectric materials, and there is no effective scheme to induce and manipulate ordered polar patterns in centrosymmetric nonpolar nanofilms due to the absence of spontaneous symmetry breaking. Here, we circumvent these limitations by utilizing the wrinkle-induced strain gradient modulation associated with flexoelectricity as a general means of inducing and manipulating ordered polar patterns in nonpolar nanofilms. Leveraging the surface instability caused by strain mismatch between oxide nanofilms and pre-strained compliant substrate, we successfully fabricate striped SrTiO3 wrinkles, where well-ordered strain gradients and corresponding periodic polar patterns are readily achieved. Through in-situ piezoresponse force microscopy experiments, we show that the generated polar patterns can be manipulated by varying strain boundaries. Furthermore, the atomistic resolution images and first-principles calculations reveal that such wrinkle-induced ordered polar patterns primarily emerge from the flexoelectric coupling between the local polarization and strain gradients. These findings provide implications for manipulating polar structures by strain gradient and flexoelectric engineering, which in turn enable the realization of nontrivial polar structures in a broader range of materials.

Multiscale study on the synergistic effect of interface heat transfer and filler structure on enhancing the thermal conductivity of boron nitride/alumina/polyurethane composites

The design and preparation of polymer composites for microelectronic package with high thermal conductivity is an important route to solve the thermal problem of electronic devices. The synergistic effect of interface heat transfer and hybrid filler structure on the enhancement of thermal conductivity in polyurethane composites was analyzed using a multiscale approach. Firstly, the interface heat transfer characteristics and strengthening mechanism of BN-TPU and Al2O3-TPU regulated by functionalization were analyzed by atomic scale calculation. Then, the thermal conductivity of BN/Al2O3/TPU composites under different interface thermal resistance, filler distribution, filler ratio and contents were studied through representative volume elements with interface layer structure. The results indicate that, due to the functionalized molecules increasing the phonon vibration overlap between the filler and matrix and thereby reducing the interface thermal resistance, the thermal conductivity of the composite materials shows an increasing trend with interface functionalization. Moreover, under the combined effects of constructing oriented BN structures, optimizing the ratio between BN and Al2O3, and regulating interface functionalization, the composites showed excellent thermal conductivity at low filler content. The research can provide important guidance for the preparation of highly thermal conductive polymer composites.

Hole Localization Induces Anionic Redox in Li-Ion Cathodes

Anionic redox is defined as the depopulation of electronic states consisting of unhybridized or minimally hybridized O 2p orbitals. In recent years, anionic redox has been investigated in great detail due its potential to increase the high-voltage capacity of Na-ion and Li-ion intercalation positive electrodes (cathodes) for batteries. However, anionic redox almost always manifests alongside a gamut of undesirable effects, from > 1 V of hysteresis, to voltage and capacity fade over hundreds of cycles. These effects have hindered the widespread utilization and commercialization of anionic redox-active cathodes. Understanding the origin and role of anionic redox is vital if we are to leverage it in high-voltage cathodes and mitigate its negative effects.Anionic redox occurs across many bulk structural motifs - from Na and Li-layered oxides to cation-disordered rocksalt-type (DRX) structures. While it was initially thought to only occur in systems with alkali metal-excess environments (such as the Li-O-Li type local configurations), it has hence been observed even in conventional stoichiometric cathodes at high states-of-charge. The crystal structure origins of anionic redox in terms of metal-oxygen decoordination and metal migrations have been well explored in the literature, a similar robust origin theory stemming from electronic structure arguments is lacking.To address this, we note that there are two manifestations of anionic redox observed in the literature - the kind that involves O-O dimerization (observed in several systems such as DRX compounds, Li2RuO3, Li- and Mn-rich NMCs, etc.) and the kind that involves localized polarons without dimers (observed in Na2Mn3O7 and Na0.6Li0.2Mn0.8O2). In attempting to reconcile both observed types of behaviour, we observe that the chief difference stems from the stabilization mechanism for adding holes to the ligand orbitals. In both cases, holes are added to ligand or ligand-dominated orbitals, with minimal to no hybridization with the adjacent transition metals. In the former kind of anionic redox, the ligand holes are stabilized by forming a sigma-like O-O bond, while in the latter, it is a weak pi-type hybridization that stabilizes the addition of ligand holes. We hypothesize that the localization of the ligand holes governs the manifestation of anionic redox in a system.In this work, we investigate this relationship between localized ligand holes and anionic redox by tuning the cation ordering in Li4FeSbO6 (LFSO). This honeycomb-ordered Li-excess material is the perfect model system to use for this study, as the electrochemical behaviour of this system features a single high-voltage plateau at 4.2 V vs. Li+/Li which is charge compensated by a novel Fe(III)/(V) redox couple. The Fe redox couple involves an electronic transition from a 3d5 majority ground state to a negative charge transfer 3d5 L 2 ground state, involving highly hybridized and localized ligand holes on Fe-O orbitals. Despite the presence of hole density on O orbitals and the presence of Li-O-Li local environments, the system cannot be classified as being anion redox active due to the contribution of the metal states to the charge compensation.However, by systematically tuning the extent of cation disorder in LFSO, we are able to convert highly metal-hybridized holes into unhybridized ligand holes, inducing anionic redox. We use a combination of soft X-ray spectroscopy, synchrotron diffraction, neutron diffraction, charge-transfer atomic multiplet calculations and density functional theory to unravel the mechanistic relationship between cation disorder, ligand hole localization and anionic redox, giving us a rational design rule for synthesizing materials with low hysteresis at high potentials. Our findings reveal the crucial role of cation disorder in promoting anionic redox.

Unveiling and Mitigating the Instability of Noble Metal-Free Oxide Electrode for PEM Water Electrolysis

Developing many sustainable energy technologies (e.g., H2O and CO2 splitting) warrants accelerating the sluggish oxygen evolution reaction (OER) efficiently and economically. However, designing noble-metal-free electrocatalysts (NMFEs) to replace noble-metal-based OER electrocatalysts is tremendously challenging in acidic electrolytes where chemical corrosion is conventionally regarded as a bottleneck factor. So far, few NMFEs reported can be an alternative to Ru-/Ir-based catalysts for acidic OER. Differernt from conventional wisdom, through monitoring the dynamics of the catalytic process during water electrolysis, we unambiguously demonstrated that electrochemical reconstruction instead of chemical corrosion dominantly degraded the OER performance of typical Mn and Co oxides as resentative NMFEs. Based on the uncovered degradation mechanism, we further developed a novel and rational method to overcome the problem of activity-stability trade-off faced by various OER electrocatalysts. Correlative operando characterizations found that our modulation method successfully suppressed the undesired surface reconstructions by mitigating the cationic/anionic redox and catalyst leaching, and meanwhile atomistic calculations revealed that the synergy of dual sites generated more favorable catalytically-active species. The resultant noble-metal-free oxide yielded a record performance among reported NMFEs, and its superior performance was also validated by the PEM water electrolyzer. This work will provide a critical reference for designing NMFEs for PEM water electrolysis.Reference:1. Jian WANG*, Controlling dynamic reconstruction chemistry for superior oxygen-evolving catalysts, Chem, 2023, 9 (7), 1645-1657.2. Jian Wang,* Ying Wang, Junsik Cho, Ting-Shan Chan, Yang Ha, Shu-Chih Haw, Cheng-Wei Kao,Yunze Zhang, Jiayi Tang,Jia Lei,Tong Liu,Siyuan Zhao, Yawen Dai, Aleksandra Baron-Wiechec, Fu-Rong Chen, Wenxiong Wang, Chang Hyuck Choi, Zongping Shao, Meng Ni, Under revision. 2024.

Comparative study of irradiation resistance for multicomponent concentrated HfNbTiZr and dilute V-4Cr-4Ti alloys irradiated with He ions

To clarify the efficiency of irradiation resistance, investigation of body-centered cubic concentrated HfNbTiZr and dilute V-4Cr-4Ti alloys, irradiated by 40 keV He ions up to 5 × 1016, 1 × 1017 and 5 × 1017 cm–2 fluences at room temperature, was carried out. Similar to V-4Cr-4Ti, HfNbTiZr possesses high phase stability and surface erosion resistance to irradiation with He ions up to 5 × 1017 cm-2. Using transmission electron microscopy, a more than 2-fold increase in overall swelling, as well as its intensification with increasing fluence was observed for HfNbTiZr compared to V-4Cr-4Ti. Combining atomistic calculations and simulations based on the Modified Embedded Atom Method interatomic potential and Density Functional Theory, the energetics of defects and helium-vacancy complexes, as well as their dynamics, were studied for alloys. It was shown that in the HfNbTiZr and dilute vanadium alloys the number of radiation-induced vacancies (v) can be comparable. According to the binding energy curves, there is a tendency for higher He accumulation in helium-vacancy complexes due to the increased He/v ratio in HfNbTiZr compared to V-4Cr-4Ti (∼1.5 versus ∼1.1). It was found that the kick-out of lattice atoms is enhanced in HfNbTiZr and is suppressed in V-4Cr-4Ti. Therefore, the more intense He bubble growth in HfNbTiZr may be due to the kick-out mechanism, which leads to a decrease in the He/v ratio and stimulates helium-vacancy complexes to trap additional He atoms. Our results can be used to improve the bubble swelling resistance in the design of new multicomponent concentrated alloys.

Theoretical analysis and predictions for the two-neutrino double electron capture of 124Xe

Abstract We provide a complete theoretical description of the two-neutrino electron capture in 124Xe, improving both the nuclear and the atomic structure calculations. We improve the general formalism through the use of the Taylor expansion method, leading to higher-order terms in the decay rate of the process. The nuclear part is treated with pn-QRPA and interacting shell model (ISM) methods. The nuclear matrix elements (NMEs) are calculated with the pn-QRPA method with isospin restoration by fixing the input parameters so that the experimental decay rate is reproduced, resulting in values significantly lower than in previous calculations. The validity of the pn-QRPA NMEs is tested by showing their values to be comparable with the ones for double-beta decay with the emission of two antineutrinos of 128,130Te, which have similar pairing features. Within the ISM, we reproduce the total experimental half-life within a factor of two and predict the capture fraction to the KK channel of about 74%. We also predict the capture fractions to other decay channels and show that for the cumulative decay to the KL1–KO1 channels, a capture fraction of about 24% could be observed experimentally. On the atomic side, calculations are improved by accounting for the Pauli blocking of the decay of innermost nucleon states and by considering all s-wave electrons available for capture, expanding beyond the K and L1 orbitals considered in previous studies. We also provide improved atomic relaxation energies of the final atomic states of 124Te, which may be used as input for background modeling in liquid Xenon experiments.

Estimating AChE inhibitors from MCE database by machine learning and atomistic calculations

Acetylcholinesterase (AChE) is one of the most successful targets for the treatment of Alzheimer's disease (AD). Inhibition of AChE can result in preventing AD. In this context, the machine-learning (ML) model, molecular docking, and molecular dynamics calculations were employed to characterize the potential inhibitors for AChE from MedChemExpress (MCE) database. The trained ML model was initially employed for estimating the inhibitory of MCE compounds. Atomistic simulations including molecular docking and molecular dynamics simulations were then used to confirm ML outcomes. In particular, the physical insights into the ligand binding to AChE were clarified over the calculations. Two compounds, PubChem ID of 130467298 and 132020434, were indicated that they can inhibit AChE.

Machine Learning-Assisted Hartree-Fock Approach for Energy Level Calculations in the Neutral Ytterbium Atom.

Data-driven machine learning approaches with precise predictive capabilities are proposed to address the long-standing challenges in the calculation of complex many-electron atomic systems, including high computational costs and limited accuracy. In this work, we develop a general workflow for machine learning-assisted atomic structure calculations based on the Cowan code's Hartree-Fock with relativistic corrections (HFR) theory. The workflow incorporates enhanced ElasticNet and XGBoost algorithms, refined using entropy weight methodology to optimize performance. This semi-empirical framework is applied to calculate and analyze the excited state energy levels of the 4f closed-shell Yb I atom, providing insights into the applicability of different algorithms under various conditions. The reliability and advantages of this innovative approach are demonstrated through comprehensive comparisons with ab initio calculations, experimental data, and other theoretical results.

Machine Learning Models for High Explosive Crystal Density and Performance.

The rate of discovery of new explosives with superior energy density and performance has largely stalled. Rapid property prediction through machine learning has the potential to accelerate the discovery of new molecules by screening of large numbers of molecules before they are ever synthesized. To support this goal, we assembled a 21,000-molecule database of experimentally synthesized molecules containing energetic functional groups. Using a combination of experimental density measurements and high throughput electronic structure and atomistic calculations, we calculated detonation velocities and pressures for all 21,000 compounds. Using these values, we trained machine learning models for the prediction of density, detonation velocity and detonation pressure. Notably, our model for crystal density surpassed the accuracy of all current models and decreased the root-mean square error (RMSE) of the previous best model by 20%. This improvement in model performance relative to past works is attributed to our handling of chiral-specified Simplified Molecular-Input Line-Entry System (SMILES) strings and introduction of a new molecular descriptor, MolDensity. To elucidate descriptor importance, we evaluated interpretable descriptors in terms of importance and compared the accuracy of a statistics-driven machine learning model against a model comprised of descriptors typically assumed to control material density. The inexpensive, yet highly accurate predictions from our models should enable creation of future artificial intelligence (AI) models that are able to screen large numbers (>106) of compounds to find the highest performing compounds in terms of crystal density, detonation velocity and detonation pressure.

Spectrum and energy levels of the high-lying singly excited configurations of Nd III. New Nd III experimental energy levels and wavelengths, with transition probability and ionisation energy calculations

We aim to accurately determine bound-to-bound transition wavelengths and energy levels of the high-lying open-shell configurations 4f$^3$7s, 4f$^3$6d, and 4f$^3$5f of doubly ionised neodymium (Nd III, $Z=60$) through high-resolution spectroscopy and semi-empirical calculations. This study is motivated by lanthanide atomic data requirements in astronomy, such those involved in investigations of kilonova spectra. Fourier transform spectra of Nd Penning and hollow cathode discharge lamps were recorded within the region 32\,500--54\,000 and grating spectra of Nd vacuum sliding sparks were recorded within the regions 820--1159 and 1600--3250 . New energy levels were found using the observed wavelengths measured accurate to a few parts in $10^8$ in Fourier transform spectra and to a few parts in $10^7$ in grating spectra. Atomic structure and transition probability calculations of Nd III were carried out using the Cowan codes, where energy parameters were adjusted to fit all known Nd III levels. Finally, Nd-rich stellar spectra were also used to aid in the analysis. In total, 355 transitions were classified from observed spectra involving 116 previously experimentally unknown energy levels of the 4f$^3$7s, 4f$^3$6d, and 4f$^3$5f configurations of Nd III, all reported here for the first time. Three newly identified levels of the 4f$^3$5d configuration and one newly identified 4f$^4$ level are also reported. Typical level energy uncertainties are 0.01 cm$^ $ for the 4f$^3$7s and 4f$^3$6d levels and 0.3 cm$^ $ for the 4f$^3$5f levels. In addition, calculated energy levels up to 130\,936 $ are presented, including eigenvector composition and calculated level lifetimes. Calculated transition probabilities and wavelengths between 1900--50\,000 are also given. Using newly established levels of the 4f$^3$7s configuration and the recently established levels of the 4f$^3$6s configuration, the ionisation energy of Nd III has been estimated at $178\,090 $. This result offers up to twice the accuracy of the most recently published value.

Spectral scheme for atomic structure calculations in density functional theory

We present a spectral scheme for atomic structure calculations in pseudopotential Kohn-Sham density functional theory. In particular, after applying an exponential transformation of the radial coordinates, we employ global polynomial interpolation on a Chebyshev grid, with derivative operators approximated using the Chebyshev differentiation matrix, and integrations using Clenshaw-Curtis quadrature. We demonstrate the accuracy and efficiency of the scheme through spin-polarized and unpolarized calculations for representative atoms, while considering local, semilocal, and hybrid exchange-correlation functionals. In particular, we find that O(200) grid points are sufficient to achieve an accuracy of 1 microhartree in the eigenvalues for optimized norm conserving Vanderbilt pseudopotentials spanning the periodic table from atomic number Z=1 to 83.

Theoretical investigation of iodine plasma through detailed electron impact excitation cross-section calculations and collisional-radiative model analysis

Abstract In the present study, we consider the electron impact excitation of neutral iodine and its application in developing a collisional-radiative model for plasma diagnostics of iodine plasma. Electron impact excitation cross- sections are calculated using fully relativistic distorted wave theory. The required atomic structure calculations for iodine are carried out using the relativistic multi-configuration Dirac-Fock method. The excitation energies obtained are reported and compared with values from the NIST database. The electron impact excitation cross-sections are calculated from the ground (5p5 2P3/2) and first- excited state (5p5 2P1/2) to the several upper fine structure levels. Our cross- section results align well with previous studies, reported by Ambalampitiya et al. [Atoms, 9, 103, 2021] using the Breit-Pauli B-spline R-matrix method. Further calculated cross-section results are incorporated into the collisional-radiative model. Our model also includes electron impact ionization, de-excitation, three- body recombination, and radiative decay. We validate our model using emission spectra from inductively coupled iodine plasma. For this purpose, we used the recorded intensities for the emission lines, 486.23 nm, 511.92 nm, 523.45 nm, 589.40 nm, and 608.24 nm are compared with those obtained from our model to calculate electron temperature and electron density of the iodine plasma.