关键词: 密度泛函理论, 烟酸-烟酸复合物, 基组重叠误差, 极化连续模型

Abstract: Nicotinic acid dimer was subjected to density functional theory calculations using B3LYP/6-311+G(d,p) basis set. Seven equilibrium isomers were located on the potential energy surface. The most stable structure isomer 1 has a strong N…H—O hydrogen-bonding interaction, and its calculated binding energy is -48.3 kJ·mol-1 corrected with basis set superposition error (BSSE).Anormal-mode analysis of the vibrations of the seven isomers was carried out. The charge transfer (CT) and their corresponding second-order interaction energies were studied by nature bond orbital (NBO) analysis. The solvent effects on the geometry of the stablest equilibrium isomer 1 were systematically studied by self-consistent reaction field polarized continuum model (PCM) technique with different dielectric constants of 1.0 (vacuum), 2.247(benzene), 10.36(dichloroethane), 20.7(acetone), 32.63(methanol), and 78.39(water). It was found that the solvent effect would significantly enhance the strength of hydrogen bond as shown by the decrease of the N…H distance. The solvent effect is obvious when ε is in 1.0-32.63 and is weak when ε exceeds 32.63.

Key words: Density functional theory, Nicotinic acid dimer, Basis set superposition error, Polarized continuummodel