Performance of Approximate Functionals A Few

No systematic attempt at comparing explicit functionals can be made here. Extensive comparisons of a wide variety of functionals can be found in Refs. [7-21]. For pure illustrative purposes only, Tables 1-5 show ground-state energies of the argon atom and of the water 

Ground-state energy, in atomic units, of the H2O molecule, obtained with some representative density functionals and basis sets. The calculation was performed with the Gaussian03 ° electronic structure package. For comparison, the total energy for H2O obtained with foil configuration interaction (FCI/cc-pVDZ) is -76.242 hartree  

Same as Table 2, for the H20 ion. FCI/cc-pVDZ total energy is -75.733 hartree.  

Same as Table 2, for the H3O+ ion. Calculated Multi-Reference Double-Excitation configuration interaction/cc-pVTZ total energy is —76.567 hartree at a ground state equilibrium geometry C3 with H-O-H angle 120 and O-H bond length 0.096 nm.  

---