Toward chemical accuracy in the computation of NMR shieldings: the PBE0 model

We present an analysis of NMR shieldings computed with a new parameter-free density functional model (PBEO) obtained combining the so-called PBE generalized gradient functional with a predefinite amount of exact exchange. A number of organic molecules as well as some transition metal oxo complexes have been considered as benchmark systems. The results obtained for H-1, C-13, N-15 and O-17 chemical shieldings are better than those delivered by the most reliable functionals including heavy parametrization and are competitive with those provided by low-order many-body perturbation techniques. The way in which the functional is derived and the lack of empirical parameters fitted to specific properties make the PBEO model a widely applicable method for quantum chemistry. (C) 1998 Elsevier Science B.V. All rights reserved.