Scaled DFT chemical shieldings

A constant scaling reducing the paramagnetic component of chemical shieldings at the B3LYP/6-311+G(2d or d, p)// B3LYP/6-311+G(d,p) level is able to reproduce experimental results in a way that improves upon other density functional methods and rivals more sophisticated ab initio approaches. Root-mean-square errors (rmse) for carbon, nitrogen, oxygen.. fluorine, phosphorus, and sulfur are found to be 2.3, 7.9, 13.2, 15.9, 22.1, and 29.7 ppm, respectively; the rmse expressed as a percentage of the shielding range varies from 1.1% to 3.2%. Anisotropies are also well reproduced. The reduction in the paramagnetic term can be associated with a constant scaling increase of the excitation energies. (C) 2003 Elsevier B.V. All rights reserved.