Comparative Quantum Chemical Study Using HF and DFT Methods in Conjunction with Different Sizes of Basis Sets

In this work, a quantum chemical study was conducted for a Schiff base derivative that had been synthesized recently by utilizing the B3LYP of Density Functional Theory and Hartree-Fock methods in conjunction with different sizes of basis sets, including 3-21g, 3-21+g, 3-21+g*, 3-21+g**, and 6-31+g(d,p). The objective of this study is to test the computational efficiency and reliability of different procedures for optimizing and energetically studying Schiff base derivatives. Different optimization parameters are studied such as the maximum force and displacement as well as their RMS values for all steps of optimizations. In addition, frontier molecular orbital study is conducted according to all the basis sets in order to figure out the gap energy and other electronic parameters for the most stable conformation of the studied Schiff base molecule. Using basis sets of a large size can make a huge difference as the case of 6-31+g(d,p), whereas no difference can be noticed between 3-21+g and 3-21+g*, specifically with Hartree-Fock method.