Molecular dynamics simulations incorporating an analytic embedded atom potential have been used to investigate the atomic structure and surface order of the Al vicinal surfaces for the temperature up to 900 K. The relaxation, mean square vibrational amplitude, and structure factor as a function of temperature, and of the terrace width for the p(100) (111) surfaces (2 p 10) are discussed. The obtained structure factor indicates that the anharmonic effect reduces with increasing terrace widths. The decrease of surface energy with increasing terrace width also supports this conclusion.

Analytic modified embedded atom method (AMEAM) type many-body potentials have been constructed for ten hcp metals: Be, Co, Hf, Mg, Re, Ru, Sc, Ti, Y and Zr. The potentials are parametrized using analytic functions and fitted to the cohesive energy, unrelaxed vacancy formation energy, five independent second-order elastic constants and two equilibrium conditions. Hence, each of the constructed potentials represents a stable hexagonal close-packed lattice with a particular non-ideal c/a ratio. In order to treat the metals with negative Cauchy pressure, a modified term has been added to the total energy. For all the metals considered, the hcp lattice is shown to be energetically most stable when compared with the fcc and bcc structure and the hcp lattice with ideal c/a. The activation energy for vacancy diffusion in these metals has been calculated. They agree well with experimental data available and those calculated by other authors for both monovacancy and divacancy mechanisms and the most possible diffusion paths are predicted. Stacking fault and surface energy have also been calculated and their values are lower than typical experimental data. Finally, the self-interstitial atom (SIA) formation energy and volume have been evaluated for eight possible sites. This calculation suggests that the basal split or crowdion is the most stable configuration for metals with a rather large deviation from the ideal c/a value and the non-basal dumbbell (C or S) is the most stable configuration for metals with c/a near ideal. The relationship between SIA formation energy and melting temperature roughly obeys a linear relation for most metals except Ru and Re.

Acoustic-phonon transmission and thermal conductance in a double-bend quantum waveguide at low temperatures are investigated with the use of the scattering matrix method. The calculated results show that the total transmission coefficient versus the reduced phonon frequency exhibits a series of resonant peaks and dips. The stop-frequency gap can be observed for certain structural parameters due to the mode-mode coupling in the bend region. The universal quantum thermal conductance and the decrease of the thermal conductance at very low temperatures can be clearly observed. However, for higher temperatures where the higher transverse modes are excited, the reduced thermal conductance K/T is proportional to temperature T. The transmission coefficient and thermal conductance sensitively depend on the geometric parameters of the double bend, which provide an efficient way to control thermal conductance artificially by adjusting the parameters of the proposed microstructures.

Using molecular dynamics simulations with an analytical embedded-atom method (MAEAM) model, the diffusion behavior of helium atoms at two Σ=5 symmetric grain boundaries of Ni was investigated in the present paper. The simulations demonstrate that the interstitial helium atoms are stable at the grain boundaries. Helium atoms in Ni lattices could diffuse easily to the grain boundary and precipitate into a cluster, which confirmed the fact that helium atoms could nucleate and grow up into bubbles at the grain boundaries. The diffusion activation energy of interstitial helium atom at grain boundaries was also determined.