Study on the Interactions Between Na+ and N-Methylacetamide and Water by the ABEEM/MM

The geometries, binding energies of [Na(H2O)(n)](+) (n = 3-8), [Na(NMA)(n)](+) (n = 3-8), [Na(NMA)(n)(H2O)(m)](+) (n+m = 4,6)(NMA = N-methylacetamide) were studied with the quantum chemical MP2/6-311++G(d, p)//B3LYP/6-31+G(d, p) level of theory and atom-bond electronegativity equalization method fused into molecular mechanics(ABEEM/MM) fluctuating charge force field. Based on the quantum chemical results, the polarizable ABEEM/MM potential energy functions of the above system were constructed, and the relative parameters were optimized and determined. The results show that the structures, binding energies, charge distributions obtained by ABEEM/MM are in good agreement with those from quantum chemical method(QM). The average absolute deviations(AAD) of distances of Na+-ligand, angles, and binding energies are less than 0.007 nm, 2.4 degrees, 8.9 kJ/mol, respectively. The relative root mean square deviations(RRMSD) of distances of Na+-ligand, angles, and binding energies are less than 3.5%, 2.0%, 12.4%, respectively. The linear correlation coefficients of the charge distributions from ABEEM/MM and QM are above 0.97.