International Journal of Modern Physics B

The intrinsic spin Hall effect has been attracting increasing theoretical and experimental interest since its discovery about two years ago. In this article, we review the main achievements in the theoretical aspect of both dissipative and nondissipative spin Hall effects in mesoscopic systems. The Landauer–Büttiker formula and Green's function approach based numerical method for the spin Hall effect is also introduced.

The binding energy of the ground state of a bound polaron near the interface of a polar-polar semiconductor heterojunction is investigated by using the Lee–Low–Pines intermediate coupling method. The influence of a triangular potential approximation of the interface, the electron-phonon and impurity-phonon interactions as well as the half-space bulk longitudinal and interface-optical phonon modes are all taken into account. We have performed numerical calculations on the GaAs/Al_xGa_1-xAs(0.2 ≤ x ≤ 0.4) heterojunction system and studied the relations between the ground state binding energy of the polaron and the impurity position, electric field strength and electron area density, respectively. It is found that with the increase in the distance between the impurity and the interface, the binding energy and the contribution of phonons reach the maximum. It is also found that the binding energy of the bound polaron increases slowly with the increase in an electric field while the total polaronic correction decreases the binding energy. When the electron area density is increased, the contribution of the interface-optical (IO) modes is greater than that of the bulk longitudinal optical (LO) mode.

A numerical investigation for the stability of the incompressible slip flow of normal quantum fluids (above the critical phase transition temperature) inside a microslab where surface acoustic waves propagate along the walls is presented. Governing equations and associated slip velocity and wavy interface boundary conditions for the flow of normal fluids confined between elastic wavy interfaces are obtained. The numerical approach is an extension (with a complex matrix pre-conditioning) of the spectral method. We found that the critical Reynolds number (Re_cr or the critical velocity) decreases significantly once the slip velocity and wavy interface effects are present and the latter is dominated (Re_cr mainly depends on the wavy interfaces).

We have developed the density functional theory (DFT) and density functional perturbation theory (DFPT) which are based both on the hybrid weighted-density approximation and on the higher-order weighted-density approximation, respectively, to study the structural and thermodynamic properties of polymer melts at interfaces. They were applied to predict the local density distributions, adsorption isotherms, surface excesses, and solvation forces of a freely jointed tangent hard-sphere chain in hard slit pores. The Wertheim's first-order perturbation theory extended by Yu and Wu [J. Chem. Phys.117, 2368 (2002)] was used to calculate the excess free energy and second-order direct correlation function due to the chain connectivity. The weight functions were calculated from the second-order direct correlation functions. The calculated results show that the DFT is in excellent agreement with the computer simulations and slightly better than the DFPT.

The success of modern electronics is built on the possibility to accurately predict system behavior by using simulation tools. This paradigm can be extended to components such as piezoelectric transducers attached to the electronics. The ability to simulate both piezoelectric transducer and electronics together renders possible effective optimizations at system level, i.e. minimizing size, cost and power consumption. In this paper a computer simulation of a combined electronics and piezoelectric transducer system is explored. The analogy between acoustic wave propagation and wave propagation in an electric transmission line is given. The simulation approach is applied to a pulser-receiver setup for the determination of speed of sound and attenuation in liquids. Experiments and simulations are made for fixed temperature and in the frequency range 1–10 MHz using ethanol, methanol, carbon tetrachloride, acetone, benzene and distilled water as test samples. Comparison shows a good agreement between simulation and experiments. Furthermore, the use of an ultrasonic simulation package allows for the development of the associated electronics to amplify and process the received ultrasonic signals.

In this study, lead zirconate titanate (Pb(Zr_0.44Ti_0.56)O₃) ceramics were fabricated with a mixed oxide synthetic route of lead oxide (PbO) and zirconium titanate (ZrTiO₄) precursors. The effects of sintering temperature on phase formation, densification and dielectric responses of the ceramics have been investigated using XRD, SEM, EDX and dielectric measurement techniques. The densification of the PZT ceramics with density of 97% theoretical density can be achieved with appropriate sintering condition without any sintering additives. The optimized sintering condition has been identified as 1225°C for 4 h. More importantly, the dielectric properties are found to improve with increasing sintering temperature and grain size. However, when sintered over 1250°C, the dielectric properties of the ceramics are seen to deteriorate as a result of PbO vaporization, ZrO₂ segregations and porosity.

The concentration dependence of atomic short range order (SRO) has been studied in Ni_100-xHf_x and Re_100-xTi_x alloys (where x = 2, 5, 10, 15, 20 at.%) using the framework of transition metal model pseudopotential (TMMP). The ordering energies and Warren–Cowley SRO parameters were calculated for the Ni-Hf and Re-Ti alloys. It was found that this model predicted the correct sign of SRO for Ni_100-xHf_x system but failed in the case of Re_100-xTi_x alloys.

In this paper, an incompressible thermohydrodynamics for the lattice Boltzmann scheme is developed. The basic idea is to solve the velocity field and the temperature field using two different distribution functions. A derivation of the lattice Boltzmann scheme from the continuous Boltzmann equation is discussed in detail. By using the same procedure as in the derivation of the discretised density distribution function, we found that a new lattice of four-velocity model for internal energy density distribution function can be developed where the viscous and compressive heating effects are negligible. This model is validated by the numerical simulation of the porous plate couette flow problem where the analytical solution exists and the natural convection flows in a square cavity.