https://mazziotti.uchicago.edu/qcdictionary/j_terms/jacobs_ladder_dft/index.html Employing the metaphor of Jacob’s Ladder, the hundreds of DFT functionals are organized into different categories that are then arranged into list from least computationally expensive to most computationally expensive, with the not-yet computed complete chemical accuracy at the top, representing “heaven”. At the base of the ladder, is the least accurate and least computationally expensive Hartree “Hell”. Hugo en-us