Duan Su-Qing

Melting and Gr?neisen parameters of NaCl at high pressure

The Buckingham potential has been employed to simulate the melting and thermodynamic parameters of sodium chloride (NaCl) using the molecular dynamics (MD) method. The constant-volume heat capacity and Gruneisen parameters have been obtained in a wide range of temperatures. The calculated thermodynamic parameters are found to be in good agreement with the available experimental data. The NaCl melting simulations appear to validate the interpretation of superheating of the solid in the one-phase MD simulations. The melting curve of NaCl is compared with the experiments and other calculations at pressure 0–30GPa range.

Molecular dynamics simulations of jet breakup and ejecta production from a grooved Cu surface under shock loading

Large-scale non-equilibrium molecular dynamics simulations are performed to explore the jet breakup and ejecta production of single crystal Cu with a triangular grooved surface defect under shock loading. The morphology of the jet breakup and ejecta formation is obtained where the ejecta clusters remain spherical after a long simulation time. The effects of shock strength as well as groove size on the steady size distribution of ejecta clusters are investigated. It is shown that the size distribution of ejecta exhibits a scaling power law independent of the simulated shock strengths and groove sizes. This distribution, which has been observed in many fragmentation processes, can be well described by percolation theory.

Dynamic Localization of a One-Dimensional Quantum Dot Array in an ac Electric Field

We investigate the dynamics of two interaction electrons confined to one-dimensional quantum dot array in an ac electric field. We find that initially localized electrons will remain localized in the absence of Coulomb interaction if the ratio of the ac field magnitude to the frequency is a root of the ordinary zero-order Bessel function. In contrast to the case without Coulomb interaction, no matter what the value is, the electrons are delocalized and the delocalization effect depends on the ratio U/omega and eaE/omega, where U is the strength of Coulomb interaction, a is the lattice constant, and E and omega are the ac held amplitude and frequency, respectively.

Atomistic simulation of fcc—bcc phase transition in single crystal Al under uniform compression

By molecular dynamics simulations employing an embedded atom model potential, we investigate the fcc-to-bcc phase transition in single crystal Al, caused by uniform compression. Results show that the fcc structure is unstable when the pressure is over 250 GPa, in reasonable agreement with the calculated value through the density functional theory. The morphology evolution of the structural transition and the corresponding transition mechanism are analysed in detail. The bcc (011) planes are transited from the fcc (111) plane and the (111) plane. We suggest that the transition mechanism consists mainly of compression, shear, slid and rotation of the lattice. In addition, our radial distribution function analysis explicitly indicates the phase transition of Al from fcc phase to bcc structure.

Intrinsic Hall effect and separation of Rashba and Dresselhaus spin splittings in semiconductor quantum wells

We have proposed a method to separate Rashba and Dresselhaus spin splittings in semiconductor quantum wells by using the intrinsic Hall effect. It is shown that the interference between Rashba and Dresselhaus terms can deflect the electrons in opposite transverse directions with a change of sign in the macroscopic Hall current, thus providing an alternative way to determine the different contributions to the spin–orbit coupling.

Dynamical properties of two-band superlattices with strong interband coupling in real space under the action of ac and dc-ac fields

Within a two-band tight-binding model driven by ac and dc-ac electric fields, using numerical methods, we investigate the dynamics of electrons and the quasi-energy spectrum of the system with strong interband coupling in real space. We find that when the bandwidth is suppressed to a value much smaller than the field frequency, the dynamical localization can exist in the system. The corresponding regions are found for the occurrence of dynamical localization in the parameter space.

Interband transitions of superlattices in arbitrary time-dependent electric fields: an analytical approach of closed-form solutions in the real space

Abstract Within a two-band tight-binding model driven by arbitrary time-dependent electric fields, we investigate the interband transitions and obtain closed-form solutions in the real space, from which we show that there are two essentially opposite evolution behaviors of the system: interband resonances and miniband localization. We also find that in weak interband coupling, as expected, the perturbative solutions are in good agreement with the exact numerical calculations.

Rabi oscillations between dissipative Bloch bands

Abstract Within a two-band tight-binding model driven by DC–AC electric fields, we investigate the dynamics of electrons with Markoffian dephasing. We find that Rabi oscillations between the Bloch bands under the resonant condition may be destroyed by scattering from lattice imperfections. Through a perturbative calculation, we also obtain the effective decay time for the approach to equal Bloch band populations under conditions of small interband coupling and in the long-time limit. The decay rate shows characteristic sharp peaks at values of the parameters that give a signature of Rabi oscillations, and quasienergy spectra display avoided crossings at the same time.

Effect of elastic scattering on photon-assisted transport in superlattices beyond the nearest-neighbor approximation

Abstract Taking into account elastic scattering, transport characteristics of superlattices driven by a DC–AC field E=E 0 +E 1 cos ωt are investigated beyond the nearest-neighbor approximation. We obtain the analytical expressions of transient current and the long-time average current. The curves of I–V characteristics show that when the frequency of elastic scattering is higher than the relaxation frequency, elastic scattering may destroy the resonant peaks.

Application of a Simple Semi-empirical Interatomic Potential Model to Phonon Density of States of Fe3Al

We proposed a simple analytical interatomic potential model by extending the framework of embedded-atom model to include the non-central three-body potentials. This model can be easily applied to treat transition metals and their alloys based on the very recently developed lattice inversion method. We used the model to calculate the phonon density of states and entropy of Fe3Al, and the results were in agreement with the experimental data.