Snapshot of 4050 atoms in a 22.4 × 22.4 × 35.8 simulation box at T = 0.7. The simulation box is stretched in the z direction so that the resulting film does not self-interact. A particles are shown in blue and B particles in red.
Temperature and thickness ranges for stable and unstable film formations. The line is a guide to the eye.
Density profiles (both species included) for films of 4050 atoms equilibrated at various temperatures. The hyperbolic tangent fit lines give four defining properties of the density profile: the liquid density ρ L , the vapor density ρ V , the location of the center of the interface z e , and the width of the interface d. The values of ρ L and d are given in Table I, as a function of temperature.
Mole fraction of B atoms as a function of film depth z for films at various temperatures. Hyperbolic tangent fit lines similar to the form given by Eq. (2) are also shown. Species segregation is evident, with a higher concentration of B atoms in the interior of the film.
The lateral (top) and normal (bottom) stress profiles plotted as a function of film depth z for films of various temperatures. Here, positive values correspond to compression and negative values to tension.
The lateral mean squared displacement for A (top) and B (bottom) particles, plotted for various layers in a film of 4050 atoms equilibrated at T = 0.7.
Lateral diffusion coefficients for films of 4050 atoms equilibrated at T = 0.5 and T = 0.7. The diffusion rate at the surface is roughly three times that of the interior.
Normalized velocity autocorrelation function (VACF) for A (top) and B (bottom) particles plotted for various layers in a film of 4050 atoms equilibrated at T = 0.7. For both types of particles, the motion near the surface differs from that in the interior of the film. In the interior, the VACF clearly becomes negative, indicating that the atoms on average rebound in the opposite direction after a short time. However, at the surface, the VACF decays monotonically to zero, indicating that, on average, the atoms on the surface do not experience this rebound. This behavior is qualitatively the same at all other temperatures examined.
Average atomic equilibrium and inherent structure potential energy assigned to an atom, as a function of the initial position before minimization, z 0, for atoms of type A and type B. The potential energy assigned to an atom is calculated by splitting pair interaction energies equally between both participating particles.
Average difference of the energy of an atom with respect to its corresponding inherent structure energy, as a function of the initial position before minimization, z 0, for atoms of type A and B. It can be seen that atoms initially at the surface descend deeper down their portion of the energy landscape upon energy minimization.
The average lateral and normal displacements that an atom undergoes during energy minimization as a function of its initial position z 0. It can be seen that atoms near the surface suffer larger lateral and normal displacements upon energy minimization than their counterparts located in the film's interior.
Fitted values of the interior density, ρ L , and interface thickness, d, for free-standing films of various temperatures, T.
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