ABSTRACT
Density functional theory (DFT)-based electronic structure calculations have provided much needed reliable, cost-effective, and flexible solution for the application of quantum mechanics to solve some of the interesting and challenging problems in chemistry. DFT is a first principle (quantum mechanical) method that evaluates the electron density directly, without finding the approximate wave function. Instead of finding the proper wave function, DFT formalism will concentrate on finding the electron density of a particular system. The basic principle of DFT is to replace the many-body electronic wavefunction with the electronic ground-state density as basic quantity. The advantage of ground-state density is a function of only three variables and a relatively simple quantity to deal with both conceptually and practically. In an important theoretical development, the physical interpretation of DFT was then offered by W. Kohn and J. Sham.
