Atomic Calculations Research Articles

Impact of random alloy fluctuations on the electronic and optical properties of (Al,Ga)N quantum wells: Insights from tight-binding calculations.

Light emitters based on the semiconductor alloy aluminum gallium nitride [(Al,Ga)N] have gained significant attention in recent years due to their potential for a wide range of applications in the ultraviolet (UV) spectral window. However, current state-of-the-art (Al,Ga)N light emitters exhibit very low internal quantum efficiencies (IQEs). Therefore, understanding the fundamental electronic and optical properties of (Al,Ga)N-based quantum wells is key to improving the IQE. Here, we target the electronic and optical properties of c-plane AlxGa1-xN/AlN quantum wells by means of an empirical atomistic tight-binding model. Special attention is paid to the impact of random alloy fluctuations on the results as well as the Al content x in the well. We find that across the studied Al content range (from 10% to 75% Al), strong hole wave function localization effects are observed. Additionally, with increasing Al content, electron wave functions may also start to exhibit carrier localization features. Overall, our investigations on the electronic structure of c-plane AlxGa1-xN/AlN quantum wells reveal that already random alloy fluctuations are sufficient to lead to (strong) carrier localization effects. Furthermore, our results indicate that random alloy fluctuations impact the degree of optical polarization in c-plane AlxGa1-xN quantum wells. We find that the switching from transverse electric to transverse magnetic light polarization occurs at higher Al contents in the atomistic calculation, which accounts for random alloy fluctuations, compared to the widely used virtual crystal approximation approach. This observation is important for light extraction efficiencies in (Al,Ga)N-based light emitting diodes operating in the deep UV.

Multiscale Modeling Unravels the Influence of Biomembranes on the Photochemical Properties of Embedded Anti-Oxidative Polyphenolic and Phenanthroline Chelating Dyes.

The embedding of caffeate methyl ester, the flavonoids luteolin and quercetin, and the o-phenanthroline and neocuproine in a liquid disordered lipid bilayer has been studied through extensive atomistic calculations. The location and the orientation of these bio-active antioxidants are explained and analyzed. While the two phenanthrolines strongly associate with the lipid tail region, the other three compounds are rather found among the head groups. The simulations showcase conformational changes of the flavonoids. Through the use of a hybrid quantum mechanics-molecular mechanics scheme and supported by a profound benchmarking of the electronic excited-state method for these compounds, the influence of the anisotropic environment on the compounds' optical properties is analyzed. Influences of surrounding water molecules and of the polar parts of the lipids on the transition dipole moments and excited-state dipole moments are weighted with respect to a change in conformation. The current study highlights the importance of the mapping of molecular interactions in model membranes and pinpoints properties, which can be biomedically used to discriminate and detect different lipid environments.

Gradient-Induced Dzyaloshinskii-Moriya Interaction.

The Dzyaloshinskii-Moriya interaction (DMI) that arises in the magnetic systems with broken inversion symmetry plays an essential role in topological spintronics. Here, by means of atomistic spin calculations, we study an intriguing type of DMI (g-DMI) that emerges in the films with composition gradient. We show that both the strength and chirality of g-DMI can be controlled by the composition gradient even in the disordered system. The layer-resolved analysis of g-DMI unveils its additive nature inside the bulk layers and clarifies the linear thickness dependence of g-DMI observed in experiments. Furthermore, we demonstrate the g-DMI-induced chiral magnetic structures, such as spin spirals and skyrmions, and the g-DMI driven field-free spin-orbit torque (SOT) switching, both of which are crucial toward practical device application. These results elucidate the underlying mechanisms of g-DMI and open up a new way to engineer the topological magnetic textures.

Implications of W-Boson Mass Anomaly for Atomic Parity Violation

We consider the implications of the recent measurement of the W-boson mass MW=80,433.5±9.4MeV/c2 for atomic parity violation experiments. We show that the change in MW shifts the Standard Model prediction for the 133Cs nuclear weak charge to QW(133Cs)=−73.11(1), i.e., by 8.5σ from its current value, and the proton weak charge by 2.7%. The shift in QW(133Cs) ameliorates the tension between existing determinations of its value and motivates more accurate atomic theory calculations, while the shift in QW(p) inspires next-generation atomic parity violation experiments with hydrogen. Using our revised value for QW(133Cs), we also readjust constraints on parameters of physics beyond the Standard Model. Finally, we reexamine the running of the electroweak coupling for the new W boson mass.

First application of a microscopic K−NN absorption model in calculations of kaonic atoms

Strong interaction energy shifts and widths in kaonic atoms are calculated for the first time using microscopic $K^- N$ + $K^- NN$ potentials derived from $K^- N$ scattering amplitudes constructed within SU(3) chiral coupled-channels models of meson-baryon interactions. The in-medium modifications of the free-space amplitudes due to the Pauli correlations are taken into account. The $K^-N+K^-NN$ potentials evaluated for 23 nuclear species are confronted with kaonic atoms data. The description of the data significantly improves when the $K^-NN$ absorption is included. To get $\chi^2$ as low as for the $K^-N+$phenomenological multi-nucleon potential an additional phenomenological term, accounting for $K^{-}-3N(4N)$ processes, is still needed. However, density dependence of this phenomenological term points out some deficiencies in the microscopic potentials and further improvements of the applied model are thus desirable. The calculated branching ratios for $K^-N$ and $K^-NN$ absorption channels in the $^{12}$C$+K^-$ atom are in reasonable agreement with the old bubble chamber data, as well as with the latest data from the AMADEUS Collaboration.

Uncovering the CO2 Capture Mechanism of NaNO3-Promoted MgO by 18O Isotope Labeling.

MgO-based CO2 sorbents promoted with molten alkali metal nitrates (e.g., NaNO3) have emerged as promising materials for CO2 capture and storage technologies due to their low cost and high theoretical CO2 uptake capacities. Yet, the mechanism by which molten alkali metal nitrates promote the carbonation of MgO (CO2 capture reaction) remains debated and poorly understood. Here, we utilize 18O isotope labeling experiments to provide new insights into the carbonation mechanism of NaNO3-promoted MgO sorbents, a system in which the promoter is molten under operation conditions and hence inherently challenging to characterize. To conduct the 18O isotope labeling experiments, we report a facile and large-scale synthesis procedure to obtain labeled MgO with a high 18O isotope content. We use Raman spectroscopy and in situ thermogravimetric analysis in combination with mass spectrometry to track the 18O label in the solid (MgCO3), molten (NaNO3), and gas (CO2) phases during the CO2 capture (carbonation) and regeneration (decarbonation) reactions. We discovered a rapid oxygen exchange between CO2 and MgO through the reversible formation of surface carbonates, independent of the presence of the promoter NaNO3. On the other hand, no oxygen exchange was observed between NaNO3 and CO2 or NaNO3 and MgO. Combining the results of the 18O labeling experiments, with insights gained from atomistic calculations, we propose a carbonation mechanism that, in the first stage, proceeds through a fast, surface-limited carbonation of MgO. These surface carbonates are subsequently dissolved as [Mg2+···CO3 2-] ionic pairs in the molten NaNO3 promoter. Upon reaching the solubility limit, MgCO3 crystallizes at the MgO/NaNO3 interface.

Atomic-scale modeling of [formula omitted] edge dislocations in UO[formula omitted]: Core properties and mobility

The dislocation properties of UO2, the main nuclear fuel material, are important ingredients to model the mechanical properties and predict nominal and accidental operations of nuclear plant reactors. However, the plastic behaviour of UO2 is complex with little known about dislocations and other extended defects. In this study, we use a combination of interatomic potential-based atomistic simulations and ab initio calculations to investigate the core structure and mobility of the 12〈110〉{001} edge dislocation, which controls the plasticity of UO2 single crystals. Various dislocation cores are obtained and compared, including the classical asymmetric Ashbee core and a so-far unreported core made of an alternation of both variants of the Ashbee core along the dislocation line. This new core, called here zigzag, is ubiquitous in molecular dynamics simulations at high temperature in the nominal-to-accidental transient regime (1600 to 2200 K). Molecular dynamics is also used to determine the velocity of the edge dislocation as a function of temperature and stress. A dislocation mobility law is adjusted from the simulations and provides an up-scaling ingredient central to the multi-scale modeling of UO2 nuclear fuel mechanical properties.

Computational modeling of the defect structure, hyperfine and magnetic properties of the Mn2+-doped magnetite of the composition MnxFe3-yO4 (y = ⅔ x)

The defect structure, hyperfine and magnetic properties of Mn2+-doped Fe3O4 of the composition MnxFe3-yO4(y=⅔x) are modeled using atomistic and DFT calculations. The atomistic simulations show the substitution of the Mn2+ ions for Fe3+ ones at the tetrahedral sites to be energetically favorable than their substitution at the octahedral sites. These Mn2+ impurities are charge-balanced by the occupation of either Mn2+ or Fe 3+ ions of interstitial tetrahedral sites. The method of GGA with on-site Coulomb interaction approximation for the exchange-correlation potential is used to calculate the electronic structure, hyperfine and magnetic moments of the structurally most preferred models. The results obtained show the model in which all the Mn2+ ions substitute for tetrahedral Fe 3+ ions with Fe3+ ions expelled to interstitial tetrahedral sites to be consistent with the observed experimental trends of the hyperfine and magnetic properties.

Electron self-energy corrections using the Welton concept for atomic structure calculations

The high level of accuracy achieved by atomic experiments in recent time has shone a spotlight on the need for a similarly high level of accuracy in atomic structure calculations, and in particular, QED prediction. A method of electron self-energy correction originally derived from the Welton idea by Lowe et al. (2013) (LCG-Welton method) has now been fully incorporated into the popular atomic structural package, GRASP2K, which we have introduced in this paper. A series of benchmark tests and results are presented, which enables the comparison of the implementations of different versions of GRASP2K, and the implementations on different platforms or operating systems. Test results presented in this paper demonstrate that these new implementations maintain the overall consistency and stability of the program across various platforms, while at the same time improve the accuracy of final energies. Our calculations for hydrogenic Lyα1,2 transitions show excellent agreement with experiment, to within less than 0.5 eV. On helium-like systems, our calculations show an improvement from the previous GRASP2K screening method. The new results from electronic self-energy contribution using the LCG-Welton method is more consistent with current standards in the literature, where they now fit within experimental variability of up to 0.1 eV. An option for users to adjust the gauge factor in the electric component of the transition rate has also been added to facilitate further investigation of this particular topic.

An Eulerian crystal plasticity framework for modeling large anisotropic deformations in energetic materials under shocks

This paper demonstrates a novel Eulerian computational framework for modeling anisotropic elastoplastic deformations of organic crystalline energetic materials (EM) under shocks. While Eulerian formulations are advantageous for handling large deformations, constitutive laws in such formulations have been limited to isotropic elastoplastic models, which may not fully capture the shock response of crystalline EM. The present Eulerian framework for high-strain rates, large deformation material dynamics of EM incorporates anisotropic isochoric elasticity via a hypo-elastic constitutive law and visco-plastic single-crystal models. The calculations are validated against atomistic calculations and experimental data and benchmarked against Lagrangian (finite element) crystal plasticity computations for shock-propagation in a monoclinic organic crystal, octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (β-HMX). The Cauchy stress components and the resolved shear stresses calculated using the present Eulerian approach are shown to be in good agreement with the Lagrangian computations for different crystal orientations. The Eulerian framework is then used for computations of shock-induced inert void collapse in β-HMX to study the effects of crystal orientations on hotspot formation under different loading intensities. The computations show that the hotspot temperature distributions and the collapse profiles are sensitive to the crystal orientations at lower impact velocities (viz., 500 m/s); when the impact velocity is increased to 1000 m/s, the collapse is predominantly hydrodynamic and the role of anisotropy is modest. The present methodology will be useful to simulate energy localization in shocked porous energetic material microstructures and other situations where large deformations of single and polycrystals govern the thermomechanical response.

Preface

The 2022 International Symposium on Semiconductor and Electronic Technology (ISSET 2022), scheduled to be held on August 12-14, 2022 in Fuzhou, China, was changed to be held as a virtual conference. ISSET 2022 promoted the development and application of theories and technologies in the fields of semiconductor and electronic technology in universities and enterprises, established business or research contact and found global partners for future careers for all the participants.During the conference, we had the honor of having invited both Prof. Zhigang Zang from Chongqing University, China and Prof. Jiangzhao Chen from Chongqing University, China to serve as our Conference General Chairs. This online conference was composed of three parts: keynote speeches, oral presentations and online Q&A discussion, attracting 60 delegates from all over the world. Firstly, keynote speakers were each allocated 30-45 minutes to hold their speeches. Then in the oral presentations, the excellent papers we had selected were presented by their authors one by one.At the beginning of the conference, five distinguished keynote speakers were invited to address their speeches. Among them, Prof. Wenli Zhou from Huazhong University of Science and Technology, China performed a thought-provoking speech on: Reservoir Computing Based on Carbon Nanotube Network. Due to the great interest on the implementation of Reservoir Computing (RC) on novel hardware, her team fabricated a physical reservoir consisting of single-walled carbon nanotubes (SWCNTs) network with phosphomolybdic acid modification and investigated its computing architecture and characteristic dynamics, demonstrating high performances in several test benches. Moreover, Prof. Junjie Qi from University of Science and Technology Beijing, China shared with us his study: In-situ Atomic Scale Studies of Structural Transitions for 2D TMDs. His team studied the phase transition and interlayer structure transition of bilayer PtSe2 under electron beam irradiation and combined atomic resolution STEM and DFT calculation to study the behavior of interlayer stacking orders and interlayer rotations in bilayer PtSe2, revealing the phase transition and interlayer structure transition mechanisms of PtSe2 at atomic scale. Their dramatic speeches had triggered heated discussion in the third part of the conference. Besides, every participant praised this conference for disseminating useful and insightful knowledge.List of Committee member is available in this pdf.

Atomistically-informed continuum modeling and isogeometric analysis of 2D materials over holey substrates

This work develops, discretizes, and validates a continuum model of a molybdenum disulfide (MoS2) monolayer interacting with a periodic holey silicon nitride (Si3N4) substrate via van der Waals (vdW) forces. The MoS2 layer is modeled as a geometrically nonlinear Kirchhoff–Love shell, and vdW forces are modeled by a Lennard-Jones (LJ) potential, simplified using approximations for a smooth substrate topography. Both the shell model and LJ interactions include novel extensions informed by close comparison with fully-atomistic calculations. The material parameters of the shell model are calibrated by comparing small-strain tensile and bending tests with atomistic simulations. This model is efficiently discretized using isogeometric analysis (IGA) for the shell structure and a pseudo-time continuation method for energy minimization. The IGA shell model is validated against fully-atomistic calculations for several benchmark problems with different substrate geometries. Agreement with atomistic results depends on geometric nonlinearity in some cases, but a simple isotropic St.Venant–Kirchhoff model is found to be sufficient to represent material behavior. We find that the IGA discretization of the continuum model has a much lower computational cost than atomistic simulations, and expect that it will enable efficient design space exploration in strain engineering applications. This is demonstrated by studying the dependence of strain and curvature in MoS2 over a holey substrate as a function of the hole spacing on scales inaccessible to atomistic calculations. The results show an unexpected qualitative change in the deformation pattern below a critical hole separation.

4-component relativistic Hamiltonian with effective QED potentials for molecular calculations.

We report the implementation of effective quantum electrodynamics (QED) potentials for all-electron four-component relativistic molecular calculations using the DIRAC code. The potentials are also available for two-component calculations, being properly picture-change transformed. The latter point is important; we demonstrate through atomic calculations that picture-change errors are sizable. Specifically, we have implemented the Uehling potential [E. A. Uehling, Phys. Rev. 48, 55 (1935)] for vacuum polarization and two effective potentials [P. Pyykkö and L.-B. Zhao, J. Phys. B: At., Mol. Opt. Phys. 36, 1469 (2003) and V. V. Flambaum and J. S. M. Ginges, Phys. Rev. A 72, 052115 (2005)] for electron self-energy. We provide extensive theoretical background for these potentials, hopefully reaching an audience beyond QED specialists. We report the following sample applications: (i) We first confirm the conjecture of P. Pyykkö that QED effects are observable for the AuCN molecule by directly calculating ground-state rotational constants B0 of the three isotopomers studied by microwave spectroscopy; QED brings the corresponding substitution Au-C bond length rs from 0.23 to 0.04pm agreement with experiment. (ii) In regard to spectroscopic constants of van der Waals dimers M2 (M = Hg, Rn, Cn, Og), QED induces bond length expansions on the order of 0.15(0.30) pm for row 6(7) dimers. (iii) We confirm that there is a significant change of valence s population of Pb in the reaction PbH4 → PbH2 + H2, which is thereby a good candidate for observing QED effects in chemical reactions, as proposed in [K. G. Dyall et al., Chem. Phys. Lett. 348, 497 (2001)]. We also find that whereas in PbH4 the valence 6s1/2 population resides in bonding orbitals, it is mainly found in nonbonding orbitals in PbH2. QED contributes 0.32 kcal/mol to the reaction energy, thereby reducing its magnitude by -1.27%. For corresponding hydrides of superheavy flerovium, the electronic structures are quite similar. Interestingly, the QED contribution to the reaction energy is of quite similar magnitude (0.35 kcal/mol), whereas the relative change is significantly smaller (-0.50%). This curious observation can be explained by the faster increase in negative vacuum polarization over positive electron self-energy contributions as a function of nuclear charge.

Exponential type orbitals with hyperbolic cosine function basis sets for isoelectronic series of the atoms Be to Ne

Abstract Exponential type orbital with hyperbolic cosine basis functions, proposed recently for Hartree–Fock–Roothaan calculations of neutral atoms, are studied in detail for the calculations of isoelectronic series of atoms from Be to Ne. Calculations are performed for the neutral and the first 20 cationic members of the isoelectronic series of each atom in its ground state. Three of the most popular exponential type orbitals (Slater type functions, B functions and ψ (α) functions with α = 2) are combined with modified hyperbolic cosine function cosh(βr + γ) to improve the basis function quality within the minimal basis sets framework. Performances of the basis functions are compared with each other by using the same number of variational parameters in them. The obtained results are also compared with numerical Hartree–Fock and extended Slater type basis set results. The presented accuracy of the minimal basis descriptions of atomic systems supports the usage of these unconventional basis functions in electronic structure and property calculations.

Electronic structures and optical characteristics of CdSbulk/CdSe nanoshells and CdSbulk/CdSe/CdS quantum-well nanoshells: Atomistic tight-binding computations

The nanoshell architectures demonstrate the unique characteristics for the promising optical gain medium and lasing applications; this is investigated here using the atomistic tight-binding model. The electronic and optical characteristics of CdSbulk/CdSe nanoshells and CdSbulk/CdSe/CdS quantum-well nanoshells with experimentally synthesized structures are determined. The atomistic signatures are sensitive with nanoshell architectures and thickness of CdSe layer. The optical band gaps become narrow with the increasing CdSe layer thicknesses due to the large quantum-confinement volume. The optical band gaps of the tight-binding theory are in the excellent consistency with the experimental observation. Encapsulating CdSe layers on CdSbulk/CdSe nanoshells mainly promote the optical properties. The electron-hole pair is comfortably generated in CdSbulk/CdSe/CdS quantum-well nanoshells with large CdSe layers. The enhancement of stokes shift and radiative lifetimes is informed with the increasing CdSe layer thicknesses. The stokes shift and radiative lifetimes of CdSbulk/CdSe/CdS quantum-well nanoshells are greater than those of CdSbulk/CdSe nanoshells.

Reducing the computational load – atomic multiconfiguration calculations based on configuration state function generators

In configuration interaction (CI) calculations the atomic wave functions are given as expansions over configuration state functions (CSFs) built on relativistic one-electron orbitals. The expansion coefficients of the configuration state functions are obtained by constructing and diagonalizing the Hamiltonian matrix. Here we show how a regrouping of the configuration state functions and the introduction of configuration state function generators (CSFGs) allow for a substantial reduction of the computational load in relativistic CI calculations. The computational methodology based on configuration state function generators, recently implemented in the General Relativistic Atomic Structure package (Grasp2018, Froese Fischer et al. (2019) [16]), is applied to a number of atomic systems and correlation models with increasing sets of one-electron orbitals. We demonstrate a reduction of the CPU time with factors between 10 and 14 for the largest CI calculations. The inclusion of the Breit interaction into the calculations is time consuming. By applying restrictions on the Breit integrals we show that it is possible to further reduce the CPU times with factors between 2 and 3, with negligible changes to the computed excitation energies. We also demonstrate that the introduction of configuration state function generators allows for efficient a priori condensation techniques, with reductions of the expansions sizes with factors between 1.5 and 2.5 and the CPU time with factors between 2.5 and 4.5, again with negligible changes to the excitation energies. In total we demonstrate reductions of the CPU time with factors up to 68 for CI calculations based on configuration state function generators, restrictions on the Breit integrals and with a priori condensed expansions compared to ordinary CI calculations without restrictions on the Breit integrals and with full expansions. Further perspectives of the new methodology based on configuration state function generators are given.

Multiscale Modeling of Solid Electrolyte Interphase Growth in Lithium-Ion Batteries

Calendar and cycle life of lithium-ion batteries (LIBs) are predominantly dictated by the passivating nature of the solid electrolyte interphase (SEI) film growth on battery anodes. Graphitic anodes exhibit stable SEI growth which enables ubiquitous commercialization of LIBs. In contrast, silicon anodes exhibit poorly passivating SEI characteristics including rapid thickness and composition changes during cycling (“breathing”) and sensitivity to electrolyte composition and surface functionalization. In this work, we develop a chemically complex continuum-level multicomponent, multiphase coupled thermodynamics-reaction-transport SEI model to unravel the mechanisms of SEI growth in LIB anodes. Atomistic calculations in conjunction with experimental datasets are utilized to ascertain the dominant decomposition pathways towards predominant SEI components like Li2EDC, Li2O, Li2CO3, LiMC, LiF etc. and inform the continuum model predictions. Furthermore, experimental voltage-hold measurements are utilized to validate the SEI model parasitic currents/composition evolution profiles enabling prediction of voltage regimes for stable SEI growth with favorable SEI composition. The development of such chemically complex SEI models will aid predictive electrolyte screening for the growth of stable and passivating SEI layers on next generation anodes like silicon.Figure 1(a) shows a schematic of the detailed SEI model incorporating species and charge transport through the pore and solid phases of the SEI for LEDC formation. Figure (b) showcases experimental leakage currents during V-hold at 100 mV and 250 mV for Li-Si half cells and the detailed SEI model fits. Figure (c) shows the SEI composition profiles predicted by the model and the formation of inner inorganic (Li2CO3, Li2O) - outer organic (LEDC) bilayer SEI. Interestingly, inorganic LiF from FEC decomposition is predicted to form throughout the SEI. Figure 1

Magnetic-translational sum rule and approximate models of the molecular Berry curvature.

The Berry connection and curvature are key components of electronic structure calculations for atoms and molecules in magnetic fields. They ensure the correct translational behavior of the effective nuclear Hamiltonian and the correct center-of-mass motion during molecular dynamics in these environments. In this work, we demonstrate how these properties of the Berry connection and curvature arise from the translational symmetry of the electronic wave function and how they are fully captured by a finite basis set of London orbitals but not by standard Gaussian basis sets. This is illustrated by a series of Hartree-Fock calculations on small molecules in different basis sets. Based on the resulting physical interpretation of the Berry curvature as the shielding of the nuclei by the electrons, we introduce and test a series of approximations using the Mulliken fragmentation scheme of the electron density. These approximations will be particularly useful in ab initio molecular dynamics calculations in a magnetic field since they reduce the computational cost, while recovering the correct physics and up to 95% of the exact Berry curvature.

Enhancing the On/Off Current Ratio in Single-Molecule FET via Destructive Quantum Interference

We investigate through atomistic calculation the electronic structure and transport properties of 3-phenylethynylene (OPE3), 7-phenylvynylene (OPV7), and [3, 3]paraCyclophane (pCp)-based molecules. We reveal and analyze the Destructive Quantum Interference (DQI) phenomenon for the pCp single-molecule junction. The provided explanation of DQI via the dominant concurrence of inter-orbital and intra-orbital interference may support DQI engineering through the chemical synthesis of ad hoc molecular channel. Furthermore, we propose a Back gate Biasing-based method for the ON/OFF CUrrent Ratio Enhancement of the single-molecule Field-Effect transistor via the control of DQI (BBB-CURE-DQI). As an important outcome of the proposed method, an ON/OFF current ratio of 103 is achieved for pCp single-molecule FET. This value is orders of magnitude larger than typical values presented in the literature. The benefit of the DQI and the effectiveness of the BBB-CURE-DQI method are finally demonstrated at the circuital level by SPICE simulations of digital inverters implemented with the investigated molecules. Our analysis and results motivate the importance of future research investment for DQI manipulation via chemical synthesis and successive control to enable single-molecule FET-based nanocomputing applications.

Combined effect of plasma screening and electric field on the He atom

The combined effect of plasma screening and electric field on the structural properties of atoms/ions is investigated with the help of the relativistic computational method. Two concepts, the ion-sphere model potential and the electric field perturbation operator, which are crucial to perform the current investigation, are introduced to solve the Dirac–Fock equations based on the self-consistent field theory. The developed algorithm is applied to calculation of the plasma-embedded He atom in the case of the field strength 0 ≤F≤ 0.1 a.u. The influences of plasma screening and applied electric field strength, separately and combined, on the energies and radiative transition properties are analyzed in detail. Our results reveal that adding shielding effect destabilizes the atomic system (reduces the energy eigenvalues), and the applied electric field counteracts this effect, thereby increasing the stability of the atomic system. On the whole, the effect of electric field on the electronic structures and spectral properties of the guest atom is a deflection shielding effect, implying that the latter effect is stronger. The present results are in good agreement with the values from the previous literature.