Cluster nucleation

The following two pictures (Figure 6.2-8a and b) were acquired at h-500 mV and at -I-450 mV vs. Cu/Cu and show that at h-450 mV vs. Cu/Cu monolayer high Cu clusters nucleate at the steps between different Au terraces. Thus, the pair of shoulders in the cyclic voltammogram is correlated with this surface process. 

The MD simulations provided the necessary thermodynamic information to obtain the equilibrium configurations of the films. Often the deposition process will produce films which are not in the equilibrium configuration, and then the problem is to determine the stablity of these films against changes in morphology. Here simulations can also be helpful, since data on the surface energies and chemical potentials of strained films can be used to calculate the probability of cluster nucleation, using classical nucleation theory. 

Why might it be important to understand cluster nucleation on an oxide surface ... 

METAL CLUSTER NUCLEATION AND GROWTH 2.1. Principles of Metal Atom Formation... 

Cluster formation under such conditions is still poorly understood. Thus far, perhaps the most complete glimpse of a cluster nucleation process was granted in the investigation of a lower temperature route to tungsten iodide clusters (55). 

While steady-state radiolysis enables the synthesis of stable metal clusters in view of their characterization and the study of their physicochemical properties, pulse radiolysis allows the real-time kinetic and spectral study of transient clusters during the aggregation mechanism. For instance, the first steps of silver clusters nucleation have been studied by the teams of A. Henglein, " E. Janata and J. Belloni using pulse radiolysis, and some of the corresponding rate constants in water have been determined ... 

A different model presented by Christiansen and Sloan is based on the fact that water molecules form labile water clusters around dissolved gas molecules. The number of water molecules in each water cluster shell depends on the size of the dissolved gas molecules, e.g. 20 for methane and 24 for ethane or 28 for propane. The clusters of the dissolved species combine to form unit cells. The formation rate of a particular hydrate structure depends on the availability of labile clusters with required coordination numbers. With a mixture of methane and propane dissolved in the liquid water phase, hydrates should form more rapidly than if either methane or propane alone are dissolved in the water phase. This cluster nucleation hypothesis is based on the assumption that the guest molecule has to be dissolved in the liquid phase before getting encased into a hydrate lattice. 

The cluster nucleation is the process of random walks in m, while the crystallite nucleation is the diffusion process in the one-dimensional size space. The probabilities of transitions from the vertex to either of the adjacent vertices depend on the free energy of clusters in different structure states. 

The Rate of Cluster Nucleation and the Kinetic Criterion of the Glass Transition... 

The rate of cluster nucleation can be found when considering the diffusion process in m as similar to the diffusion in the crystallite size space, which is leading to crystallization. The frequency ratio of atom attachment to and detachment from the cluster is generally calculated by using the equations of detailed balance. Then the expression for the rate of cluster nucleation is obtained as [6.12]... 

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