Basis set effect on hydrogen bond stabilization energy estimation of the Watson-Crick type nucleic acid base pairs using medium-size basis sets: single point MP2 evaluations at the HF optimized structures

The basis set effect in evaluation of hydrogen bond energies of the Watson-Crick type base pairs between adenine (A) and uracil (U) and between guanine (G) and cytosine (C) was studied from 6-31G to 6-311++G(3df,p) basis set at the second-order Moller-Plesset (MP2) levels of theory using the structures optimized at the Hartree-Fock (HF) level of theory. Both the optimized structures around the hydrogen bonds and the hydrogen bond energies fluctuated largely depending on whether or not one set of the d-type polarization functions was set on the heavy atoms. The effects of the second and third sets of the d-type and first set of f-type polarization functions on the heavy atoms were smaller. Almost the same tendency was observed in the A-U and the G-C base pairs in the fluctuation of hydrogen bond energy depending on the basis set. The hydrogen bond energies of A-U and G-C base pairs calculated at MP2/6-31++(2d',p')//HF/6-31G(d,p) were in good agreement with the result of MP2/6-311+G(3df,p)//HF/6-311++G(3d,p).