Introduction to Statistical Physics pp 61-83 | Cite as

# Microcanonical Ensemble

Chapter

## Abstract

According to the fundamental postulate of statistical mechanics, the

**accessible microscopic states of a closed system in equilibrium are equally probable.**The number of microscopic states of a thermodynamic fluid, with energy*E*, volume*V*, and number of particles*N*, in the presence of a set {*X*_{ i }} of internal constraints, is given by Ω =Ω (*E*,*V*,*N*; {*X*_{ i }}). For example, in the previous chapter we looked at a system of two simple fluids subjected to an internal constraint given by an adiabatic, fixed, and impermeable wall (see figure 4.1). The probability*P*({*X*_{ i }}) of finding a system subjected to the set of constraints {*X*_{ i }} is proportional to Ω (*E*,*V*,*N*; {*X*_{ i }}), that is,$$P(\{ {X_i}\} ) \propto \Omega (E,V,N;\{ {X_i}\} ).$$

(4.1)

## Keywords

Composite System Thermodynamic Limit Isothermal Compressibility Entropy Representation Internal Constraint
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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## Copyright information

© Springer Science+Business Media New York 2001