Incomplete melting of the Si(100) surface from molecular-dynamics simulations using the Effective-Medium Tight-Binding model

Al(110) has been studied for temperatures up to 900 K via ensemble density-functional molecular dynamics. The strong anharmonicity displayed by this surface results in a negative coefficient of thermal expansion, where the first interlayer distance decreases with increasing temperature. Very shallow channels of oscillation for the second-layer atoms in the direction perpendicular to the surface support this anomalous contraction, and provide a novel mechanism for the formatio...

We studied the dynamics of the reconstructed Si (111) surface using a total-energy-vibrational-spectrum approach based on a non-orthogonal tight-binding Hamiltonian. We first established the size of the supercell sufficient to yield a reliable determination of surface parameters by the structural optimization. The site density of vibrational states (SDOS) for the semi-infinite system (the optimized slab on top of the bulk) was then calculated using the method of real space Gr...

The coupling energies between the buckled dimers of the Si(001) surface were determined through analysis of the anisotropic critical behavior of its order-disorder phase transition. Spot profiles in high-resolution low-energy electron diffraction as a function of temperature were analyzed within the framework of the anisotropic two-dimensional Ising model. The validity of this approach is justified by the large ratio of correlation lengths, $\xi_\parallel^+/\xi_\perp^+ = 5.2$...

We present an atomistic-continuum model to simulate ultrashort laser-induced melting processes in semiconductor solids on the example of silicon. The kinetics of transient non-equilibrium phase transition mechanisms is addressed with a Molecular Dynamics method at atomic level, whereas the laser light absorption, strong generated electron-phonon non-equilibrium, fast diffusion and heat conduction due to photo-excited free carriers are accounted for in the continuum. We give a...

The structure of the Cu(110) surface is studied at high temperatures using a combination of lattice-gas Monte Carlo and molecular dynamics methods with identical many-atom interactions derived from the effective medium theory. The anisotropic six-vertex model is used in the interpretation of the lattice-gas results. We find a clear roughening transition around T_R=1000K and T_R/T_M=0.81. Molecular dynamics reveals the clustering of surface defects as the atomistic mechanism o...

The high temperature surface properties of alkali halide crystals are very unusual. Through molecular dynamics simulations based on Tosi-Fumi potentials, we predict that crystalline NaCl(100) should remain stable without any precursor signals of melting up to and even above the bulk melting point $T_m$. In a metastable state, it should even be possible to overheat NaCl (100) by at least 50 K. The reasons leading to this lack of surface self-wetting are investigated. We will b...

Melting behaviors of aluminum (111) perfect/nonperfect surfaces, characterized by structure ordering parameter, have been investigated by classical molecular dynamics simulation with embedded atom method potential. Al (111) perfect surface has a superheating temperature above bulk Al melting point Tm, in this work, by about 80 K. Al nonperfect (111) surface has somewhat different local lattice structure from that on (111) perfect surface. Al nonperfect (111) surfaces tempt to...

An optimized interatomic potential has been constructed for silicon using a modified Tersoff model. The potential reproduces a wide range of properties of Si and improves over existing potentials with respect to point defect structures and energies, surface energies and reconstructions, thermal expansion, melting temperature and other properties. The proposed potential is compared with three other potentials from the literature. The potentials demonstrate reasonable agreement...

The high-temperature properties of the Al(111) surface are studied by molecular-dynamics simulation. This surface does not melt below the bulk melting point, but can be superheated. Superheating of metal surfaces has been recently observed in several experiments. A molecular-dynamics study of the structural properties reveals how after going through the superheating regime melting occurs over the whole crystal in a narrow temperature range. The temperature dependence of the s...

We extend Expanded Wang-Landau (EWL) simulations beyond classical systems and develop the EWL method for systems modeled with a tight-binding Hamiltonian. We then apply the method to determine the partition function and thus all thermodynamic properties, including the Gibbs free energy and entropy, of the fluid phases of Si. We compare the results from quantum many-body (QMB) tight binding models, which explicitly calculate the overlap between the atomic orbitals of neighbori...