Dynamics of nanoscale droplets

Several aspects of the dynamical behavior of nanometer-sized liquid drops have been investigated using molecular dynamics computer simulations. The liquids consist of chains of lengths 2-100 with Lennard-Jones and nonlinear elastic interactions, comprising drops made of O(100 000) atoms with radius O(10 nm), placed on an atomistic substrate. We simulate the solidification of a liquid drop on a substrate as the latter is cooled, and observe a smooth contraction and smoothing process but no dimple formation. If instead we simulate heating of the substrate, the drop evaporates, and we find a decrease on contact angle in the partially wetting case. in accord with recent predictions. Last, we consider the coalescence of two such droplets, either spontaneously or when pushed together, to study shape evolution scaling laws and to document a rapid internal structural reequilibration. Aside from the intrinsic novelty associated with the small scale of these systems, the results illustrate the relation between atomic scale interactions and macroscopic continuum properties of materials.