Link between K-absorption edges and thermodynamic properties of warm-dense plasmas established by improved first-principles method

A precise calculation that translates shifts of X-ray K-absorption edges to variations of thermodynamic properties allows quantitative characterization of interior thermodynamic properties of warm dense plasmas by X-ray absorption techniques, which provides essential information for inertial confinement fusion and other astrophysical applications. We show that this interpretation can be achieved through an improved first-principles method. Our calculation shows that the shift of K-edges exhibits selective sensitivity to thermal parameters and thus would be a suitable temperature index to warm dense plasmas. We also show with a simple model that the shift of K-edges can be used to detect inhomogeneity inside warm dense plasmas when combined with other experimental tools

Extended First-Principles Molecular Dynamics Method From Cold Materials to Hot Dense Plasmas

An extended first-principles molecular dynamics (FPMD) method based on Kohn-Sham scheme is proposed to elevate the temperature limit of the FPMD method in the calculation of dense plasmas. The extended method treats the wave functions of high energy electrons as plane waves analytically, and thus expands the application of the FPMD method to the region of hot dense plasmas without suffering from the formidable computational costs. In addition, the extended method inherits the high accuracy of the Kohn-Sham scheme and keeps the information of elec- tronic structures. This gives an edge to the extended method in the calculation of the lowering of ionization potential, X-ray absorption/emission spectra, opacity, and high-Z dense plasmas, which are of particular interest to astrophysics, inertial confinement fusion engineering, and laboratory astrophysics

Residue cross sections of 50^{50}Ti-induced fusion reactions based on the two-step model

$^{50}$Ti-induced fusion reactions to synthesize superheavy elements are studied systematically with the two-step model developed recently, where fusion process is divided into approaching phase and formation phase. Furthermore, the residue cross sections for different neutron evaporation channels are evaluated with the statistical evaporation model. In general, the calculated cross sections are much smaller than that of $^{48}$Ca-induced fusion reactions, but the results are within the detection capability of experimental facilities nowadays. The maximum calculated residue cross section for producing superheavy element $Z=119$ is in the reaction $^{50}$Ti+$^{247}$Bk in $3n$ channels with $\sigma_{\rm res}(3n)=0.043$ pb at $E^{*}$ = 37.0 MeV.Comment: 6 pages, 7 figure

On the String Equation of the BKP Hierarchy

The Adler-Shiota-van Moerbeke formula is employed to derive the $W$-constraints for the $p$-reduced BKP hierarchy constrained by the string equation. We also provide the Grassmannian description of the string equation in terms of the spectral parameter.Comment: 17 page

First-Principles Calculation of Principal Hugoniot and K-Shell X-ray Absorption Spectra for Warm Dense KCl

Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. Pressure ionization and thermal smearing are shown as the major factors to prevent the deviation of pressure from global accumulation along the Hugoniot. In addition, cancellation between electronic kinetic pressure and virial pressure further reduces the deviation. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the $3p$ electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter

Nondestructive testing of marine protective coatings using terahertz waves with stationary wavelet transform

Terahertz wave propagation in marine protective coatings and its non-destructive testing (NDT) capability were studied by the finite difference time domain (FDTD) method. The FDTD model was used to calculate the propagation and reflection of THz radiation from marine protective coatings. The reflected terahertz waves could be employed in coating thickness analysis of the paint layers. In order to clearly identify the interface between antifouling and anticorrosive coatings, stationary wavelet transform (SWT) approach was applied to decompose the obtained terahertz impulse functions into approximation and detail coefficients; SWT detail coefficients were used for the feature extraction of the coating thickness. SWT provides a more accurate identification of salient features in a signal, such as the weak feature between antifouling and anticorrosive coatings. We found that the developed model and SWT-based algorithms could be used to evaluate the occurrence of defects beneath the coatings (e.g., paint-off and corrosion defects). The proposed method provides the solution for coating thickness of marine protective coatings and it would benefit the effective maintenance to avoid coating failure and facilitate marine protective coating design. Therefore, non-destructive testing and evaluation of marine protective coating system by terahertz waves with SWT could be recommended for engineering applications

Diisonicotinium penta­chloridoanti­monate(III) monohydrate

In the title compound, (C6H6NO2)2[SbCl5]·H2O, the SbIII atom exhibits a distorted square-pyramidal coordination geometry. The crystal structure is stabilized by inter­molecular N—H⋯Cl, N—H⋯O, O—H⋯Cl and O—H⋯O hydrogen bonds, forming an extended three-dimensional network