D. Y. Sun

Development of new interatomic potentials appropriate for crystalline and liquid iron

Two procedures were developed to fit interatomic potentials of the embedded-atom method (EAM) form and applied to determine a potential which describes crystalline and liquid iron. While both procedures use perfect crystal and crystal defect data, the first procedure also employs the first-principles forces in a model liquid and the second procedure uses experimental liquid structure factor data. These additional types of information were incorporated to ensure more reasonable descriptions of atomic interactions at small separations than is provided using standard approaches, such as fitting to the universal binding energy relation. The new potentials (provided herein) are, on average, in better agreement with the experimental or first-principles lattice parameter, elastic constants, point-defect energies, bcc–fcc transformation energy, liquid density, liquid structure factor, melting temperature and other properties than other existing EAM iron potentials.

Generalized simulated annealing algorithm and its application to the Thomson model

Abstract Based on the Tsallis statistics, the generalized simulated annealing algorithm (GSA) is tested and developed. Studies on the Thomson model show that the GSA is more efficient than the classical simulated annealing and the fast simulated annealing. The fluctuation of energy is reduced drastically. The convergence to the global minimum is fast. We believe the GSA algorithm is a powerful method to find the global minimum in more realistic problems, like the equilibrium structure of big clusters.

A new constant-pressure molecular dynamics method for finite systems

We present a new method for constant-pressure molecular dynamics simulation which is parameter free. This method is especially appropriate for finite systems in which a periodic boundary condition does not apply. Simulations on carbon nanotubes and Ni nanoparticles clearly demonstrate the validity of the method, from which we can also easily obtain the equations of states for a finite system under external pressure.

Cluster on the fcc(111) surface: structure, stability and diffusion

The static and dynamical properties of a highly symmetric cluster on a fcc(111) surface are studied using the molecular-dynamics method. We find that the cluster can only be stable on the surface up to a certain temperature much lower than the melting temperature of the corresponding isolated cluster; the surface can strongly change the thermal properties of the cluster. The fast diffusion of the cluster is attributed to the rolling of cluster as a whole on the surface, and the dependence of diffusion constants on the structural mismatch is also studied.

A molecular-dynamics study of the anisotropic surface-melting properties of Al(110)

Surface melting of Al(110) was studied by molecular dynamics simulations with a well tested glue potential. We found that the surface began to disorder above 600 K via the formation of adatoms and vacancies. While bulk melting was observed at 945 K (experimental melting point is 933.5 K), the top four atomic layers were found to become liquid-like just before the bulk melts. Both the diffusion constants and the structure factors confirmed that surface melting of Al(110) was anisotropic, with random atom motion faster in the [110] direction than in the [100] direction. On the other hand, in agreement with recent experimental observations [M. Polcik et al., Phys. Rev. Lett. 78 (1997) 491], our calculations showed the presence of a residual order preferentially along the [110] direction via the presence of intact [110] atom chain segments, even above 900 K.

The structure and stability of clusters on surfaces

The structure and the stability of clusters on surfaces are simulated by using the constant-energy molecular-dynamics method. The necessary condition for a cluster to be supportable on a surface is studied. It is found that the lattice mismatch has a strong effect on the stability of clusters on surfaces; the structures obtained are surface dependent. The thermal stability of the supported clusters on surfaces is also investigated.

Interatomic potential fitted for lead

Abstract By using the recently improved generalized-simulated-annealing algorithm and the molecular dynamics method, we numerically fit an interatomic potential for lead. The potential obtained can correctly reproduce many physical properties of lead in crystalline and non-crystalline phases. The surface energy and surface relaxation obtained are in good agreement with the experimental results. The melting point predicted by this potential is very close to the experimental data. The present potential is used to study the surface melting and liquid structure; good agreement with experimental results is observed.