In this paper, we consider antireflective properties of textured surfaces for all texture size-to-wavelength ratios. Existence and location of the global reflection minimum with respect to geometrical parameters of the texture is a subject of our study. We also investigate asymptotic behavior of the reflection with the change of the texture geometry for the long and short wavelength limits. As a particular example, we consider silicon-textured surfaces used in solar cells technology. Most of our results are obtained with the help of the finite-difference time-domain (FDTD) method. We also use effective medium theory and geometric optics approximation for the limiting cases. The FDTD results for these limits are in agreement with the corresponding approximations.
The electric microfield distributions at the location of an ion have been calculated using a coupling parameter integration technique for Li + plasma proposed by Ortner et al. [4] and Molecular Dynamics simulations. Electric microfield distributions are studied in a frame of the Hellmann-Gurskii-Krasko pseudopotential model, taking into account the quantum-mechanical effects and the ion shell structure [34]. The screened Hellmann-GurskiiKrasko pseudopotential taking into account not only the quantum-mecanical effects, the ion shell structure but screening field effects has been derived by means of Bogoljubow method [40] and [42]. The screened pseudopotential is represented by a Fourier transform. For the Hellmann-Gurskii-Krasko pseudopotential model the results obtained for the microfield in the framework of the Ortner model are found in a good agreement with the Molecular Dynamics simulations.
Despite its promise as a method for the simulation of time-dependent many-body quantum mechanics problems, wave packet molecular dynamics (WPMD) is limited in its use by wave packet spreading when applied to dense plasma systems. We employ more accurate methods to determine if spreading really occurs and how WPMD can be improved. A scattering process involving a single dynamic electron interacting with a periodic array of statically screened protons is used as a model problem for the comparison. We compare the numerically exact split operator Fourier transform (SOFT) method, the Wigner trajectory method (WTM), and the time dependent variational principle (TDVP). Within the framework of the TDVP, we use the standard variational form of WPMD, the single Gaussian wave packet (WP). We then generalize this form to include multiple Gaussian for the single electron as in the split WP propagation method. Wave packet spreading is predicted by all methods, so it is not the source of the unphysical behavior of WPMD at high temperatures.Instead, the Gaussian WP's inability to correctly reproduce breakup of the electron's probability density into localized density near the protons is responsible for the deviation from more accurate predictions. Extensions of WPMD must include a mechanism for breakup to occur in order to yield dynamics that lead to accurate electron densities.
Staircasing of media properties is one of the intrinsic problems of the finite-difference time-domain method, which reduces its accuracy. There are different approaches for solving this problem, and the most successful of them are based on correct approximation of inverse permittivity tensor epsilon(-1) at the material interface. We report an application of this tensor method for conductive and dispersive media. For validation, comparisons with analytical solutions and various other subpixel smoothing methods are performed for the Mie scattering from a small sphere.
The problem of wave packet broadening in the method of wave packet molecular dynamics simulations of electron–ion nonideal plasmas is discussed. It is shown that when using a harmonic restrictive potential for the packet widths, simulation results depend strongly on the constraint parameter. Two new approaches to constraining the packet broadening in a less stringent way are analyzed: periodic boundary conditions for widths and a dynamic constraint, based on filtering close particle collisions. These different ways to localize electrons are compared by calculating the dynamical plasma collision rate and the particle pair distribution functions.
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