Hydrogen bonding and stacking interactions of nucleic acid base pairs: A density-functional-theory based treatment

We extend an approximate density functional theory (DFT) method for the des cription of long-range dispersive interactions which are normally neglected by construction, irrespective of the correlation function applied. An empi rical formula, consisting of an R-6 term is introduced, which is appropriat ely damped for short distances; the corresponding C-6 coefficient, which is calculated from experimental atomic polarizabilities, can be consistently added to the total energy expression of the method. We apply this approxima te DFT plus dispersion energy method to describe the hydrogen bonding and s tacking interactions of nucleic acid base pairs. Comparison to MP2/6-31G*(0 .25) results shows that the method is capable of reproducing hydrogen bondi ng as well as the vertical and twist dependence of the interaction energy v ery accurately. (C) 2001 American Institute of Physics.