Is the Lamb shift chemically significant?

The contribution of the Lamb shift to the atomization energies of some prototype molecules, BF3, AlF3, and GaF3 is estimated by a perturbation procedure. It is found to be in the range 3-5% of the one-electron scalar relativistic contribution to the atomization energy. The maximum absolute value is 0.2 kcal/mol for GaF3. These sample calculations indicate that the Lamb shift is probably small enough to be neglected for energetics of molecules containing light atoms if the target accuracy is 1 kcal/mol, but for higher accuracy calculations and for molecules containing heavy elements it must be considered. (C) 2001 Elsevier Science B.V. All rights reserved.