Comparative Atomic Charges on Na+-(H2O)n (n=1-6) Clusters

The performance of our mean gradient charge (MGC) concept was systematically investigated by adopting Na+-(H2O)(n) (n = 1-6) model clusters. The Mulliken charges are sensitive to the choice of theories and basis sets, and ChelpG charges abnormally behave with the system size. MGC and atoms-in-molecules (AIM) show small mean standard deviations (similar to 0.02) with the choice of the theory and the basis set. However, an unpredictable value was found in AIM predictions. Both natural population analysis (NPA) and MGC yielded smooth and monotonic curves as a function of the system size. Therefore, MGC appears to have desirable properties in the consistent and reliable predictions of atomic charges.