Role of electron correlation in the quantum‐mechanical calculations of the coulomb interaction energy in the DNA base pairs

Abstract

The intermolecular electronic correlation contributions to the Coulomb component of the nucleic acid base interaction energy are estimated. The Coulomb energy is evaluated with the use of atomic monopoles, which are determined from the rr-electronic densities calculated by the SCF method and by employing partially or completely optimized APSG wave functions. When the correlation is thus taken into account, a systematic decrease in atomic charges occurs; this effect is considerable only if an optimized orbital set is used. As a result, the Coulomb interaction energy due to the rr-electronic atoms decreases from -1.13 to -0.85 kcal/mol for the AT pair and from -7.15 to -4.61 kcal/mol for the GC pair.