利用浮动电荷力场对N-甲基乙酰胺水溶液的分子动力学模拟

利用原子键电负性均衡结合分子力场方法(ABEEM/MM)对N-甲基乙酰胺(NMA)分子的水溶液体系进行了分子动力学模拟. 与经典的力场模型相比, 该方法中的静电势包含了分子内和分子间的静电极化作用, 以及分子内电荷转移影响, 同时加入了化学键等非原子中心电荷位点, 合理体现了分子中的电荷分布. 相对其它极化力场模型, 该模型具有计算量较小的特点. 在该模型下对NMA纯溶液和其水溶液体系进行了分子动力学模拟, 得到的径向分布函数、汽化热和偶极矩等物理量与实验值和其它极化力场方法符合很好, 合理描述了溶质与溶剂之间的静电极化和分子内的电荷转移.

Molecular Dynamic Simulation of N-Methylacetamide Aqueous Solution by Fluctuating Charge Force Field

The ABEEM/MM (atom-bond electronegativity equalization fused into molecular mechanic) fluctuating charge force field was used in molecular dynamic simulation for N-methylacetamide (NMA) aqueous solution. The electrostatic potential is obtained from the fixed atomic-center charges for the classi- cal force field. In the ABEEM/MM model, comparing to the classical force field, the partial charges are al- lowed to fluctuate in the same molecule in response to the environment. In order to describe the charge population reasonably, the important non-atomic-center charge sites (chemical bond and lone pair) are added into this model. The CPU time is not increased larger than other polarized force field. The resulting data of molecular dynamic simulation were analyzed for pure NMA and its aqueous solution, such as the radial dis- tribution function, heat of vaporization, dipole moments, etc. All in all, the relevant quantities are well in agreement with those of the corresponding experimental and other polarized model. The charge transfers of intramolecule and the polarization between solvent and solute are reasonably described with the ABEEM/MM model.