A STUDY OF SMALL SYSTEMS CONTAINING H-ATOMS AND O-ATOMS USING NONLOCAL FUNCTIONALS - COMPARISONS WITH AB-INITIO AND EXPERIMENT

Structures and energies have been calculated for HO, H2O, O-2, HO2, H2 O2, and O-3 molecules using the nonlocal functionals PW86, PW91, B-P86 , and B-LYP with the goal of obtaining their atomization energies. Res ults were compared with those from highly correlated methods and exper iment. It was found that all nonlocal functionals perform similarly to or better than correlated methods MP4 and QCI (using relatively equiv alent basis sets). All nonlocal energies were self-consistently calcul ated using the optimized geometries for each functional. None of the r esults contain any empirical correction except those inherent to some of the functionals. Increasing the size of the basis set when using th e nonlocal functionals does not lead to any significant improvement of the energies and surprisingly it worsens the results for one of the f unctionals. (C) 1994 John Wiley & Sons, Inc.