The functional of the fourth rung of Jacob's ladder is called hybrid functional because of the incorporation of exact exchange terms from the Hartree-Fock formalism and correlation terms from other areas such as experiments or theoretical calculations. One of the most powerful and highly accurate hybrids functional is B3LYP. The mathematical expression for the B3LYP functional is given below, which consists of Becke-three-parameters exchange functional and Lee-Yang-Parr correlation functional .