Exponential type orbitals description

As a foreword it must be said, perhaps constructing a too late homage to the brilliant contribution of professor Boys to Quantum Chemistry, that the first description of cartesian exponential type orbitals (CETO) was made thirty years ago by Boys and Cook [1], One can probably think this fact as a consequence of the evolution of Boys s thought on the basis set problem and to the incipient ETO-GTO dilemma, which Boys has himself stated ten years earlier [2a]. 

Finally, DFT methods are one-dimensional just like HF methods, and increasing the size of the basis set allows a better and better description of the KS orbitals. Since the DFT energy depends directly on the electron density, it has an exponential convergence with respect to basis set size, analogously to HF methods, and a polarized triple zeta type basis usually gives results close to the basis set limit. 

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