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Abstract: The growth of uniform thin films on foreign substrates is impeded by several morphological instabilities. Hill-and-valley structures are formed and enhanced during sputter deposition where surface height perturbations have an opportunity to grow to large amplitudes. We show via kinetic Monte Carlo (kMC) simulations that while surface roughness can be partially controlled by changing growth conditions, such as substrate temperature, the diffusion of particles over step edges plays a very important role in determining both surface roughness and the density of the films. Our kMC simulations provide a way to evaluate the strength of surface instabilities during sputter deposition of thin films. [Copyright &y& Elsevier]

Abstract: In order to provide insight into coarsening mechanisms of pentaerythritol tetranitrate (PETN), we performed kinetic Monte Carlo (KMC) simulations of evaporation from the predominantly exposed (110) surface. Our KMC simulations show that different surface structures, such as islands and straight step segments, move in very different ways during evaporation. We show that closed surface structures (e.g. islands or convex step edges) evaporate faster than open features (e.g. straight or concave step edges) due to inexhaustible sources of kink sites in their edges. From Arrhenius plots of step velocities we obtained activation energies for evaporation that are in excellent agreement with predictions from a model and recent experimental data. The effects of surface diffusion on evaporation rates are discussed within a rate theory model. [Copyright &y& Elsevier]

Abstract: Starting from an accurate inter-atomic potential we develop a simple scheme of generating an “on-lattice”molecular potential of short range, which is then incorporated into a lattice Monte Carlo code for simulating size and shape evolution of nanocrystallites. As a specific example, we test such a procedure on the morphological evolution of a molecular crystal of interest to us, e.g., Pentaerythritol Tetranitrate, or PETN, and obtain realistic facetted structures in excellent agreement with experimental morphologies. We investigate several interesting effects including, the evolution of the initial shape of a “seed” to equilibrium configuration, and the variation of growth morphology as a function of the rate of particle addition relative to diffusion. [Copyright &y& Elsevier]