## CHAPTER 4

## Elements of Statistical Mechanics and Principles of Quantum Mechanics

#### 4.1 Introduction

Statistical mechanics mainly deals with the distribution of identical, distinguishable and indistinguishable particles of a system in different states of the system. The number of ways, in which the particles can be arranged in different energy states depends on the distinguishability of the particles. Here we are going to see three different types of distributions: (i) Maxwell–Boltzmann distribution, (ii) Fermi–Dirac distribution and (iii) Bose–Einstein distribution.

#### 4.2 Phase space

Let us consider a system consisting of a large number of particles. The state of a particle at an instant can be represented with three position and three momentum ...