**General Characteristics of Nucleation:**
– Nucleation is a stochastic process.
– Nucleation of a new phase follows exponential decay if not occurred.
– Classical nucleation theory estimates nucleation rates.
– Nucleation initiates various processes like amyloid aggregate formation.
– Microtubules in cells exhibit nucleation and growth.
**Types of Nucleation and Factors Affecting Nucleation:**
– Heterogeneous nucleation often dominates homogeneous nucleation.
– Purified water freezes at lower temperatures than impure water.
– Nucleation barrier decreases on surfaces with smaller contact angles.
– Nucleation can start at the surface of a liquid.
– Gold nanoparticles show crystal phase nucleation at the liquid-gold surface.
**Computer Simulation and Theoretical Studies on Nucleation:**
– Classical nucleation theory assumptions and limitations.
– Modern computers calculate exact nucleation rates for simple models.
– Comparisons with classical theory show reasonable approximation.
– Uncertainty exists for complex molecules crystallizing out of solution.
**Applications and Observations of Nucleation in Various Fields:**
– Nucleation in cloud formation and cloud dynamics.
– Nucleation in boiling processes and its effects on surfaces.
– Importance of nucleation in materials science and industrial applications.
– Experimental observations on crystal nucleation in small volumes.
**Advanced Studies and Research on Nucleation:**
– Crystal nucleation studies and experimental findings.
– Nucleation kinetics and studies on crystal formation.
– Nanoparticle nucleation mechanisms and stability limits.
– References to notable works in nucleation theory and applications.
In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. For example, if a volume of water is cooled (at atmospheric pressure) below 0 °C, it will tend to freeze into ice, but volumes of water cooled only a few degrees below 0 °C often stay completely free of ice for long periods (supercooling). At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures nucleation is fast, and ice crystals appear after little or no delay.
Nucleation is a common mechanism which generates first-order phase transitions, and it is the start of the process of forming a new thermodynamic phase. In contrast, new phases at continuous phase transitions start to form immediately.
Nucleation is often very sensitive to impurities in the system. These impurities may be too small to be seen by the naked eye, but still can control the rate of nucleation. Because of this, it is often important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at nucleation sites on surfaces in the system. Homogeneous nucleation occurs away from a surface.