On the application of conventional quantum chemistry methods of computation to states perturbed by the continuous spectrum

The suitability for calculating accurately electron affinities (positive or negative) of the QCISD(T), of the B3LYP density functional, and of similar methods is examined critically, using as examples the B-3P, D-1, and Be-2P states discussed recently by Bauschlicher [Int. J. Quantum Chem. 66, 285 ( 1998)]. It is pointed out that for negative ion states above the threshold the framework of their calculation must be based on theory which accounts c orrectly for the contribution of the open channels. (C) 1999 John Wiley & S ons, Inc.