Wave Calculations Research Articles

Adsorption of alkali and alkaline-earth metal atoms on stanene: A first-principles study

This paper presents a study on the adsorption of alkali and alkaline-earth metal atoms on single-layer stanene with different levels of coverage using first-principles plane wave calculations within spin-polarized density functional theory. The most favorable adsorption site for alkali atoms (Li, Na, K) were found to be the hollow site similar to other group IV single-layers, but the case of alkaline-earths on stanene is different from silicene and germanene. Whereas Mg and Ca are bound to stanene at hollow site, the bridge site is found to be energetically favorable for Be adatom. All adsorbed atoms are positively charged due to the charge transfer from adatom to stanene single-layer. The semimetallic bare stanene become metallic except for Be adsorption. The Beryllium adsorption give rise to non-magnetic semiconducting ground state. Our results illustrate that stanene has a reactive and functionalizable surface similar to graphene or silicene.

Development of an ASIC preamplifier for electromagnetic sensor probes for monitoring space electromagnetic environments

Multipoint observations of plasma waves are essential for separating spatial and temporal variations of a plasma turbulence. Miniaturization and high environmental (temperature and radiation) robustness are key requirements for scientific instrument design toward a sensor network consisting of palm-sized probes. With increasing these demands, a preamplifier for the 3-axis loop antenna of an electromagnetic sensor probe has been developed by using application-specific integrated circuit (ASIC) technology with a 0.25-μm complementary metal-oxide-semiconductor process. In the present study, a new temperature compensation method is proposed by using the open-loop gain of the ASIC preamplifier with a bandgap reference (BGR) circuit. Usually, the gain is characterized by the closed-loop gain, which is governed by the accuracy of the polysilicon resistances in a chip. The open-loop gain is characterized by the effective transconductance of the ASIC preamplifier, which often has a negative temperature dependence. The temperature dependence of the gain can be dramatically improved by using the temperature-compensated BGR circuit to cancel out the negative dependence of the transconductance. The temperature dependence of the gain was about $$-0.01$$ dB/ $$^\circ $$ C in the frequency range within the closed-loop bandwidth. On the other hand, the temperature dependence of the gain at 60 kHz operating with the open-loop gain was improved from $$-39\times 10^{-3}$$ to $$-2.6\times 10^{-3}$$ dB/ $$^\circ $$ C by using the temperature-compensated BGR circuit. Moreover, the radiation robustness for the total ionizing dose (TID) level is evaluated by irradiation with gamma rays from cobalt-60. The ASIC preamplifier is not sensitive to TID effects when a thin gate oxide is used. The ASIC preamplifier showed a high radiation tolerance to at least a total ionizing dose level of 400 krad(Si). Finally, the effectiveness of the ASIC preamplifier is evaluated on the basis of a virtual sounding rocket experiment using theoretical calculations of LF standard electromagnetic waves. Fundamental issues (miniaturization, low-noise performance, and high environmental robustness) are solved by the presented ASIC preamplifier. The success in developing the high robustness ASIC preamplifier leads to a future mission using a lot of palm-sized probes in space.

Full potential linear augmented plane wave calculations of Electronic and Optical properties in ZnO

         In this work we present self-consistent calculations for the electronic and optical properties of Zinc oxide. A theoretical investigation of the electronic properties (band structure, density of charge and contour map) and optical properties (refractive index, absorption coefficient, dielectric constants and reflectivity) of Zinc oxide semiconductor ZnO. A full-potential linearized augmented plane-wave (FPLAPW) method was used within the density functional theory (DFT) along with the generalized gradient approximation (GGA96) exchange correlation potential. The results are compared with the experimental data available and some other theoretical work. We found that the GGA approximation yields only a small improvement to the band gap, however, if we allow for a rigid shift of the band structure, the so-called scissor’s operator, the optical properties are excellently reproduced.

Reply to “Comment on ‘Correlation and relativistic effects in U metal and U-Zr alloy: Validation ofab initioapproaches’ ”

In the Comment by S\oderlind et al. [Phys. Rev. B 90, 157101 (2014)], the authors argue that (1) density functional theory (DFT), especially with all-electron methods, already models U metal and U-Zr alloy accurately; and (2) $\mathrm{DFT}+U$ results calculated at ${U}_{\mathrm{eff}}=1.24$ for volume, enthalpy, and magnetic moments that they select from our study [Phys. Rev. B 88, 235128 (2013)] suggest adding the Hubbard $U$ potential in $\mathrm{DFT}+U$ reduces accuracy compared to DFT. With respect to argument (1) by S\oderlind et al., we argue that previously neglected and very recent experimental data suggest that DFT in S\oderlind's full-potential linear muffin-tin orbital calculations [Phys. Rev. B 66, 085113 (2002)] still models the bulk modulus and elastic constants of \ensuremath{\alpha}U with errors considerably larger than other related elements, e.g., most transition metals. In addition, we demonstrate that the assertion by S\oderlind et al. that our DFT results are not satisfactory because deficiency exists in our projector augmented wave calculation is unfounded. With respect to argument (2) by S\oderlind et al., we argue that they have inappropriately focused on just one phase [the bcc phase \ensuremath{\gamma}(U,Zr)], neglecting the other phases which represent the majority of our evidence; made overgeneralizations based on results at only one ${U}_{\mathrm{eff}}$ value of 1.24 eV; and supported their argument with inaccurate assertions that $\mathrm{DFT}+U$ predicts for \ensuremath{\gamma}(U,Zr) an unprecedentedly large positive volume of mixing and an enthalpy of mixing that is inconsistent with the experimental miscibility gap. We therefore hold to our original conclusion that the accuracy of DFT for modeling U and U-Zr has room for improvement and $\mathrm{DFT}+U$ is a good candidate.

The transmitted and reflected waves due to the incidence of a forced wave on a junction

The airborne sound transmission through a plate below its critical frequency is dominated by forced waves even though the plate vibration is dominated by freely propagating waves. This article studies whether the transmission of the two wave types is different at a junction. It is shown in this article that it is not possible to separately calculate in a meaningful way the intensity of a forced incidence wave and its freely propagating reflected wave in the medium from which incidence occurs because the cross terms in the intensity calculation for the combined waves, which vanish when the incident wave is freely propagating, do not vanish when the incident wave is forced. This means that it is not possible to define a transmission factor for forced incident waves. Thus, the transmitted intensity must be calculated as a function of the mean square wave amplitude of the forced wave.

Band structure computation of in-plane elastic waves in 2D phononic crystals by a meshfree local RBF collocation method

In this paper, the band structures of in-plane elastic waves in two-dimensional (2D) phononic crystals are calculated by using a meshfree local radial basis functions (RBF) collocation method. In order to improve the stability of the local RBF collocation method, special techniques suggested in our previous work for anti-plane waves are further improved and extended for calculating the primary field quantities and their normal derivatives required by the treatment of the boundary conditions in the local RBF collocation method for computing the band structures of the in-plane elastic waves in 2D phononic crystals. The developed meshfree local RBF collocation method for the band structure calculations of in-plane elastic waves propagating in 2D phononic crystals is validated by using the corresponding numerical results obtained with the finite element method (FEM). The band structures of different material combinations or acoustic impedance ratios, different filling fractions, various lattice forms and scatterer shapes are computed numerically to show the accuracy and the efficiency of the meshfree local RBF collocation method for computing the band structures of in-plane elastic waves in 2D phononic crystals.

Energy levels, lifetimes and radiative data of Ba XXVI

We report an extensive and an elaborate theoretical study of atomic data for Ba XXVI by considering Singlet, Doublet and Triplet (SDT) electron excitations within N-shell and single excitations from N-shell to O-shell. We have calculated energy levels and lifetimes for lowest 110 fine structure levels by using Multi-configuration Dirac–Fock method (MCDF). We have also considered Quantum Electrodynamics (QED) and Breit corrections in our calculations. We have presented the radiative data for electric and magnetic dipole (E1, M1) and quadrupole (E2, M2) transitions among lowest 110 levels. We have made comparisons of our calculated excitation energies and EUV (Extreme Ultraviolet) transition wavelengths with experimentally observed energy levels and wavelengths and achieved good agreement. We have also computed energy levels by performing similar relativistic distorted wave calculations using Flexible Atomic Code (FAC). Additionally, we have provided new atomic data for Ba XXVI which are not published elsewhere in the literature. We believe that our results may be beneficial in fusion plasma research and astrophysical investigations and applications.

Experimental Observation of Bohr's Nonlinear Fluidic Surface Oscillation.

Niels Bohr in the early stage of his career developed a nonlinear theory of fluidic surface oscillation in order to study surface tension of liquids. His theory includes the nonlinear interaction between multipolar surface oscillation modes, surpassing the linear theory of Rayleigh and Lamb. It predicts a specific normalized magnitude of 0.416η2 for an octapolar component, nonlinearly induced by a quadrupolar one with a magnitude of η much less than unity. No experimental confirmation on this prediction has been reported. Nonetheless, accurate determination of multipolar components is important as in optical fiber spinning, film blowing and recently in optofluidic microcavities for ray and wave chaos studies and photonics applications. Here, we report experimental verification of his theory. By using optical forward diffraction, we measured the cross-sectional boundary profiles at extreme positions of a surface-oscillating liquid column ejected from a deformed microscopic orifice. We obtained a coefficient of 0.42 ± 0.08 consistently under various experimental conditions. We also measured the resonance mode spectrum of a two-dimensional cavity formed by the cross-sectional segment of the liquid jet. The observed spectra agree well with wave calculations assuming a coefficient of 0.414 ± 0.011. Our measurements establish the first experimental observation of Bohr’s hydrodynamic theory.

Cohesive properties of (Cu,Ni)–(In,Sn) intermetallics: Database, electron-density correlations and interpretation of bonding trends

This paper presents a systematic and comparative study of the composition and volume dependence of the cohesive properties for a large group of Me–X intermetallic phases (IPs) with Me=Cu,Ni and X=In,Sn, which are of interest in relation with the design of lead-free soldering (LFS) alloys. The work relies upon a database with total-energy versus volume information developed by using projected augmented waves (PAW) calculations. In previous papers by the current authors it was shown that these results account satisfactorily for the direct and indirect experimental data available. In the present work, the database is further expanded to investigate the composition dependence of the volume (V0), and the composition and volume dependence of the bulk modulus (B0) and cohesive energy (Ecoh). On these bases, an analysis is performed of the systematic effects of replacing Cu by Ni in several Me–X phases (Me=Cu,Ni and X=In,Sn) reported as stable and metastable, as well as various hypothetical compounds involved in the thermodynamic modeling of IPs using the Compound-Energy Formalism. Moreover, it is shown that the cohesion-related quantities (B0/V0)½ and (Ecoh½/V0) can be correlated with a parameter expressing the number of valence electrons per unit volume. These findings are compared in detail with related relations involving the Miedema empirical electron density at the boundary of the Wigner–Seitz cell. In view of the co-variation of the cohesive properties, Ecoh is selected as a key property and its composition and structure dependence is examined in terms of a theoretical view of the bonding which involves the hybridization of the d-states of Cu or Ni with the s and p-states of In or Sn, for this class of compounds. In particular, a comparative analysis is performed of the DOS of various representative, iso-structural Me–X compounds. Various effects of relevance to understand the consequences of replacing Cu by Ni in LFS alloys are highlighted and explained microscopically for the first time.

Comparison between Full Wave and Ray-Tracing Calculations to Examine Scenarios for Electron Bernstein Wave Heating in LHD

Comparison between Full Wave and Ray-Tracing Calculations to Examine Scenarios for Electron Bernstein Wave Heating in LHD

New Cu(II) complex with acetylpyridine benzoyl hydrazone: experimental and theoretical analysis

This work describes the synthesis and the crystal structure of a copper(II) complex – [Cu(HL)(NO3)2]·H2O – based on 2-acetylpyridine-benzoylhydrazone ligand (HL). In the complex, copper(II) is five-coordinate with two nitrate ligands and a tridentate NNO-donor. The copper center has square pyramidal geometry with an axial nitrate and the equatorial positions occupied by another nitrate and the hydrazone. Besides X-ray studies, the complete structural characterization includes elemental analysis, IR, and UV–vis spectroscopy. Plane wave and localized basis set calculations support the distorted square pyramidal geometry. Theoretical calculations using several DFT functionals were used to study the performance of functionals for this complex. Solvent effect was studied on optimized geometries allowing better support to its spectroscopic data. Noncovalent π⋯π stacking interactions were also analyzed.

Numerical identification of tsunami boulders and estimation of local tsunami size at Ibaruma reef of Ishigaki Island, Japan

AbstractTsunami boulders deposited along the coast constitute important geological evidence for paleotsunami activity. However, boulders can also be deposited by large storm waves. Although several sedimentological and theoretical methods have been proposed to differentiate tsunami and storm wave affected boulders, no appropriate numerical method exists for their differentiation. Therefore, we developed a new numerical scheme to differentiate tsunami and storm wave boulders for coastal boulders on Ishigaki Island, Japan. In this area, tsunami and storm waves have emplaced numerous boulders on the reef and the coast. By conducting numerical calculations of storm waves in this region, we estimated the size of a storm wave that can explain the maximum clast size distribution of boulders on the reef. Consequently, we showed that a wave with a combination of 8 m in initial wave height and 10 s period can satisfy the above conditions when we assume mean sea level. In contrast to the boulders on the reef, all boulders deposited along the shore are heavier than the calculated possible maximum clast size distribution by the storm wave. Therefore, we confirmed these boulders as being of tsunami origin. Results of previous studies showed that they were most likely deposited or reworked by the 1771 Meiwa tsunami. Then, using the tsunami boulders, we numerically estimated the wave period and amplitude of the 1771 Meiwa tsunami, which should have had a 4–5 min period and 5.6–5.9, 6.3–7.0 m amplitude, respectively. Using the proposed scheme, it is possible to differentiate tsunami and storm wave boulders and estimate the size of past storm waves and tsunami waves, although it is noteworthy that there are exceptions for which the scheme cannot be applied.

Phase transition and optoelectronic properties of MgH2

In this article, structural and electronic properties of MgH2 have been studied. The aim behind this study was to find out the ground state crystal structure of MgH2. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P42/mnm (α-MgH2), Pa3 (β-MgH2) and Pbcn (γ-MgH2). It has been found that the ground state structure of MgH2 is α-MgH2. The present study shows that α-MgH2 transforms into γ-MgH2 at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH2 transforms into β-MgH2 at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH2 is insulating and its optical conductivity is around 6.0 eV. The α-MgH2 and γ-MgH2 are anisotropic materials while β-MgH2 is isotropic in nature.

Polarization measurement of dielectronic recombination transitions in highly charged krypton ions

We report linear polarization measurements of x rays emitted due to dielectronic recombination into highly charged krypton ions. The ions in the He-like through O-like charge states were populated in an electron beam ion trap with the electron beam energy adjusted to recombination resonances in order to produce $K\alpha$ x rays. The x rays were detected with a newly developed Compton polarimeter using a beryllium scattering target and 12 silicon x-ray detector diodes sampling the azimuthal distribution of the scattered x rays. The extracted degrees of linear polarization of several dielectronic recombination transitions agree with results of relativistic distorted--wave calculations. We also demonstrate a high sensitivity of the polarization to the Breit interaction, which is remarkable for a medium-$Z$ element like krypton. The experimental results can be used for polarization diagnostics of hot astrophysical and laboratory fusion plasmas.

Revisiting Ir(CO)3Cl

We return to an old puzzle – the short metal–metal separation and electrical conductivity of the apparently unoxidized one-dimensionally stacked structure of a d8 Ir(I) complex, Ir(CO)3Cl. One would expect neither a short Ir–Ir distance of 2.84Å, nor metallicity in an unoxidized stacked square-planar d8 array. We build up dimer, trimer, one-dimensional polymer and model 3-dimensional structures, in both molecular and extended structure plane wave calculations. The short Ir–Ir separation in the polymer, with a substantial contribution of 6pz–5dz2 bonding to it, is obtained without any oxidation. There is computational evidence for an important level crossing in the polymer. The metallicity remains unexplained, but likely arises from partial oxidation. And that remains an outstanding experimental issue.

Topological Magnon Bands in a Kagome Lattice Ferromagnet.

There is great interest in finding materials possessing quasiparticles with topological properties. Such materials may have novel excitations that exist on their boundaries which are protected against disorder. We report experimental evidence that magnons in an insulating kagome ferromagnet can have a topological band structure. Our neutron scattering measurements further reveal that one of the bands is flat due to the unique geometry of the kagome lattice. Spin wave calculations show that the measured band structure follows from a simple Heisenberg Hamiltonian with a Dzyaloshinkii-Moriya interaction. This serves as the first realization of an effectively two-dimensional topological magnon insulator--a new class of magnetic material that should display both a magnon Hall effect and protected chiral edge modes.

Relation between Left Atrial Remodeling in Young Patients with Cryptogenic Stroke and Normal Inter-atrial Anatomy.

Background and PurposeTo investigate an association between left atrial (LA) structural and P wave dispersion (PWD) during sinus rhythm, and electrical remodeling in cryptogenic stroke (CS) patients.MethodsForty CS patients and 40 age- and sex-matched healthy controls were enrolled. P wave calculations were based on 12-lead electrocardiography (ECG) at a 50-mm/s-paper speed with an amplitude of 10 mm/mV. Difference between the maximum and minimum P wave duration was the P wave dispersion (PWD=Pmax-Pmin). LA deformation was evaluated by speckle tracking echocardiography within 3 days of the acute event.ResultsPWD was 30.1±7.0 ms and 27.4±3.5 ms in CS and control group (P=0.02), whereas LA maximum volume index [LAVImax] was 20.4±4.5 mL/m2 and 19.9±2.4 mL/m2 in CS and control group, respectively (P = 0.04). While global peak LA strain was [pLA-S] (LA reservoir function) 41.4 ± 6.3% and 44.5 ± 7.1% in CS and control group, (P = 0.04), global peak late diastolic strain rate values [pLA-SRa] (LA pump function) were 2.5 ± 0.4% and 2.9 ± 0.5% in CS and control group, respectively (P = 0.001). A mild and a strong negative correlation between global pLA-S and LAVImax (r=-0.49; P<0.01), and between PWD and global pLA-S (r = -0.52; P < 0.01), respectively, was observed in CS.ConclusionsIncreased PWD is associated with impaired LA mechanical functions and enlargement, and involved in the pathophysiology of AF or an AF-like physiology in CS.

Dirac R-matrix and Breit–Pauli distorted wave calculations of the electron-impact excitation of W44+

With construction of ITER progressing and existing tokamaks carrying-out ITER-relevant experiments, accurate fundamental and derived atomic data for numerous ionization stages of tungsten (W) is required to assess the potential effect of this species upon fusion plasmas. The results of fully relativistic, partially radiation damped, Dirac R-matrix electron-impact excitation calculations for the ion are presented. These calculations use a configuration interaction and close-coupling expansion that opens-up the 3d-subshell; this does not appear to have been considered before in a collision calculation. As a result, it is possible to investigate the arrays, [3d104s2–3d94s24f] and [3d104s2–3d94s4p4d], which are predicted to contain transitions of diagnostic importance for the soft x-ray region. Our R-matrix collision data are compared with previous R-matrix results by Ballance and Griffin as well as our own relativistically corrected, Breit–Pauli distorted wave and plane-wave Born calculations. All relevant data are applied to the collisional-radiative modelling of atomic populations, for further comparison. This reveals the paramount nature of the 3d-subshell transitions from the perspectives of radiated power loss and detailed spectroscopy.

Simulation of forward and backward waves evolution of few-cycle pulses propagating in an optical waveguide with dispersion and cubic nonlinearity of electronic and electronic-vibration nature

Numerical method for calculation of forward and backward waves of intense few-cycle laser pulses propagating in an optical waveguide with dispersion and cubic nonlinearity of electronic and electronic-vibration nature is described. Simulations made with the implemented algorithm show that accounting for Raman nonlinearity does not lead to qualitative changes in behavior of the backward wave. Speaking about quantitative changes, the increase of efficiency of energy transfer from the forward wave to the backward wave is observed. Presented method can be also used to simulate interaction of counterpropagating pulses.

Calculation of energy levels, lifetimes and radiative data for La XXIX to Sm XXXIV

We present the most comprehensive atomic data for La XXIX to Sm XXXIV with single electron excitation from M-shell to N-shell and N-shell to higher shells. We have presented energy levels, lifetimes and radiative data using Multi-configuration Dirac–Fock (MCDF) method for the lowest 27 states belonging to the configuration 3d104l (l=0,1,2,3), 3d105l (l=0,1,2,3,4), 3d106l (l=0,1,2,3,4) and 3d94s2. We have also considered relativistic effects by incorporating quantum electrodynamics (QED) and Breit corrections. We have made comparisons of our presented results with available theoretical as well as experimental results and a good agreement is achieved. Further, we have also reported energy levels by performing distorted wave calculations with fully relativistic flexible atomic code (FAC). The calculations match well with MCDF results. Additionally, we have investigated the effect of nuclear charge on transition wavelength and radiative rates for strong Extreme Ultraviolet (EUV) transitions from n=4→4. We believe that our reported data in this work may be useful in various applications of lanthanide ions related to broad area of research such as applied physics, laser physics and astrophysics etc.