In general, a basis set is the linear combination of numerical functions (called basis functions) which are used for the representation of the electron wave function . In DFT, the Kohn-Sham orbitals are represented with an appropriate basis set for the practical application in computers. Any basis functions, e.g., Gaussian, exponential, polynomial, plane-wave, spline, Slater type orbitals, numeric atomic orbitals, etc. may be used to construct the basis set depending on the certain criteria as mentioned below ;