Abstract

An assembly of a few to thousands of atoms or molecules is referred to as a cluster. This chapter exclusively deals with atomic clusters and their classifications based on the nature of bonding and the number of constituents. The size effect, surface phenomena, and variation of properties with the size of atomic clusters have also been discussed. The difficulties in cluster experiments have been highlighted. Various theoretical methods to study the clusters have been mentioned, with the main focus on the density functional theory (DFT). The accuracy of various DFT methods and choosing appropriate methods have been particularly discussed. Finally, the way to perform DFT-based studies on clusters is also explored. This chapter provides a brief introduction to what the book is all about.