Introduction

In this chapter the historical perspective of phase transitions is presented including the principles of phase transitions in macroscopic systems due to Gibbs. The phenomenon of fragmentation which has been observed in small system phase transitions is introduced. Comparisons between the first order phase transitions in small, intermediate and large scale systems are made based on the concept introduced by S.A. Berry. A number of experimental examples of phase transitions in small systems are introduced. It is argued that a better understanding of phase transitions in small systems will help the development of self-assembly which is the fundamental of bottom up nanotechnology.

Principles of phase separations / transitions are well-defined and formulated in the macroscopic limit [1-6]. The macroscopic limit is defined when the number of atoms and molecules in a large system is of the order of 10 ²³ or more which is theoretically at infinite limit, known as thermodynamic limit [( N and V) ? ? but N/Y=finite]. Most of the existing theories of fluids, solids, mixtures and phase transitions are developed for systems at the thermodynamic limit using, mainly, canonical or grand-canonical ensembles [7,8]. However, for small systems consisting of limited number of particles, principles governing the separation of phases is not well...