[en] Using Medium Energy Ion Scattering, we have studied the structural and vibrational properties of a number of clean and chemisorbed metal surfaces. The work presented in this thesis is mainly of a fundamental nature. However, it is believed that an atomistic understanding of the forces that affect surface structural and vibrational properties can have a beneficial impact on a large number of areas of applied nature. We find that the surface structure of Cu(001) follows the common trend for metal surfaces, where a small oscillatory relaxation exists beginning with a slight contraction in the top layer. In addition, the surface vibrational amplitude is enhanced (as s usually the case) by ∼80%. A detailed analysis of our data shows an unexpected anisotropy of the vibrational amplitude, such that the out-of-plane vibrational amplitude is 30% smaller than the in-plane vibrational amplitude. The unexpected results may imply a large tensile stress on Cu(001). Upon adsorption of 1/4 of a monolayer of S, a p(2 x 2)-S/Cu(001) surface is created. This submonolayer amount of S atoms makes the surface bulk-like, in which the anisotropy of the surface vibrations is removed and the first interlayer contraction is lifted. By comparing our model to earlier contradictory results on this controversial system. We find excellent agreement with a recent LEED study. The presence of 0.1 monolayer of Ca atoms on the Au(113) surface induces a drastic atomic rearrangements, in which half of the top layer Au atoms are missing and a (1 x 2) symmetry results. In addition, the first interlayer spacing of Au(113) is significantly reduced. Our results are discussed in terms of the energy balance between competing surface electronic charge densities

[en] Soft-mode theory based on DIFFOUR model for ferroelectric interaction and the mean-field theory of high spin Ising model for antiferromagnetic interaction are used to investigate the ferroelectric, antiferromagnetic, magnetoelectric properties in ferroelectromagnetic lattice in which the ferroelectric order and antiferromagnetic order coexist simultaneously below a certain temperature. Ferroelectric polarization, spin moment, and magnetoelectric susceptibility as well, as a function of temperature for system, are calculated and compared with the different coupling coefficient. It is found that an anomaly appears in curve of the polarization susceptibility as a function of temperature due to the coupling between the ferroelectric and antiferromagnetic orders in the ferroelectromagnetic lattice. At the same time, we also considered the influence of magnetoelectric effect on polarization susceptibility by applying the external field including electric and magnetic

[en] The transverse-field Ising model is successfully applied to the Ba_xSr_1-xTiO₃ system. An impurity-induced paraelectric-ferroelectric phase transition is found for proper parameters. An explanation is offered for the results of the susceptibility χ(x, T), the transition temperature T_m (x), the spontaneous polarization (P ) versus x and versus T, the field dependence of χ(x, T) and that of the polarization (P ) versus E for x, 0.2 ≤ x ≤ 0.95

[en] A critical rule without free parameters to estimate the size-dependent enhancement or reduction of phase transition pressure ΔP_e(D) for phase transitions of nanocrystals is established where D denotes the size of nanocrystals. ΔP_e(D) function is determined by D, surface energy γ, surface stress f and gram-atom volume V_g of the two transition phases. Also, the individual contributions of γ and f on ΔP_e(D) can be separated. Our model predictions agree well with the corresponding experimental and theoretical results. This model is of fundamental significance in understanding the essence of size-dependent pressure induced phase transition and guiding the experimental scientists to estimate their results. - Highlights: • Size-dependent phase transition pressure for nanocrystals is discussed. • Variation tendencies of phase transition pressure can be determined. • Surface energy, surface stress and gram-atom volume are the decisive parameters. • Individual contributions of surface energy and surface stress are clarified. • Model predictions agree well with the experimental and theory results

[en] We present a new expression for the five-dimensional static Kaluza–Klein black hole solution with squashed S³ horizons and three different charge parameters. This black hole solution belongs to D=5, N=2 supergravity theory, its spacetime is locally asymptotically flat and has a spatial infinity R×S¹↪S². The form of the solution is extraordinary simple and permits us very conveniently to calculate its conserved charges by using the counterterm method. It is further shown that our thermodynamical quantities perfectly obey both the differential and the integral first laws of black hole thermodynamics if the length of the compact extra-dimension can be viewed as a thermodynamical variable

[en] Banerjee and Majhi's recent work shows that black hole's emission spectrum could be fully reproduced in the tunneling picture, where, as an intriguing technique, the Kruskal extension was introduced to connect the left and right modes inside and outside the horizon. Some attempt, as an extension, was focused on producing the Hawking emission spectrum of the (charged) Reissner-Nordstroem black hole in the Banerjee-Majhi treatment. Unfortunately, the Kruskal extension in their observation was so badly defined that the ingoing mode was classically forbidden traveling towards the center of black hole, but could quantum tunnel across the horizon with the probability Γ=e^{-πω₀/κ₊}. This tunneling picture is unphysical. With this point as a central motivation, in this paper we first introduce such a suitable Kruskal extension for the (charged) Reissner-Nordstroem black hole that a perfect tunneling picture can be provided during the charged particle's emission. Then, under the new Kruskal extension, we revisit the Hawking emission spectrum and entropy spectroscopy as tunneling from the charged black hole. The result shows that the tunneling method is so universally robust that the Hawking blackbody emission spectrum from a charged black hole can be well reproduced in the tunneling mechanism, and its induced entropy quantum is a much better approximation for the forthcoming quantum gravity theory. (orig.)

[en] In this paper, a model of multiferroic heterostructure is constructed by growing an epitaxial piezoelectric film on a magnetostrictive layered manganite single crystal. By considering the efficient mechanical coupling at the interface, the magnetoelectric (ME) effect, especially for magnetically induced polarization of the multiferroic film, has been theoretically studied by combining the modified constitutive equations with the Landau-Ginsberg-Devonshire (LGD) thermodynamic theory, where the influence of residual strain, spontaneous polarization and magnetostriction were considered. The calculated results show that large magnetic field-induced polarization could be produced in ferroelectric film due to a gigantic magnetically induced in-plane constraint and an enhanced elastic coupling interaction, which is consistent with Green's function technique analysis. The ME effect peaks at the ferromagnetic transition temperature of the manganite. Comparison with experimental data of multilayered samples reveals good interface coupling between the magnetostrictive phase substrate and epitaxial ferroelectric film. The calculations are in broad agreement with the available experimental results

[en] We propose a nonvolatile memory based on carbon nanotubes (CNTs) serving as the key building blocks for molecular-scale computers and investigate the dynamic operations of a double-walled CNT memory element by classical molecular dynamics simulations. The localized potential energy wells achieved from both the interwall van der Waals energy and CNT-metal binding energy make the bistability of the CNT positions and the electrostatic attractive forces induced by the voltage differences lead to the reversibility of this CNT memory. The material for the electrodes should be carefully chosen to achieve the nonvolatility of this memory. The kinetic energy of the CNT shuttle experiences several rebounds induced by the collisions of the CNT onto the metal electrodes, and this is critically important to the performance of such an electrostatically telescoping CNT memory because the collision time is sufficiently long to cause a delay of the state transition

[en] The particle and energy reflection coefficients of fusion α-particles with energies from 100 eV to 100 keV from the surfaces of some first wall materials are calculated by the improved bipartition model for light ion transport. The influence of the surface barrier upon the reflection of α-particles is investigated. The calculated data also include the dependence of the reflection coefficients on the angle of incidence. The comparisons of present results with those of relevant experiments and Monte Carlo simulations show that the bipartition model may yield reasonably accurate reflection data for light ions. (author)

[en] Using entropy density of Dirac field near the event horizon of a rectilinear non-uniformly accelerating Kinnersley black hole, the law for the thermal radiation of black hole is studied and the instantaneous radiation energy density is obtained. It is found that the instantaneous radiation energy density of a black hole is always proportional to the quartic of the temperature on event horizon in the same direction. That is to say, the thermal radiation of a black hole always satisfies the generalized Stefan–Boltzmann law. In addition, the derived generalized Stefan–Boltzmann coefficient is no longer a constant, but a dynamic coefficient related to the space–time metric near the event horizon and the changing rate of the event horizon in black holes. (general)