Unlike wave mechanics that solve the Schrodinger equation by approximating wave function, density functional theory (DFT) uses density of electrons, thereby reducing the many body quantum mechanics to a one body problem. The challenge in quantum mechanics then is to find the approximation for true wavefunction, while in DFT, the goal is to find the best approximation of exchange-correlation functional Exc(?) that enclose all the unknown parts. However, unlike wave mechanics where there is a clear systematic strategy to improve the approximate wave function, there is no such guideline in DFT. In fact, the quality of DFT calculation depends solely on the accuracy of the chosen exchange-correlation functional. Therefore, it is interesting to compare the performance of various functional like LDA, GGA and hybrid functional with experimental value. This worksheet uses the Maple Quantum Chemistry Toolbox.