基于分子模拟的分子力场对沥青体系典型组分适应性研究

Adaptability of molecular force fields to typical components in asphalt systems based on molecular simulation

分子模拟技术在沥青微观机理研究中的应用广泛,但尚未建立适用于沥青的分子结构理论和力场。文中以量子力学计算结果为基准,比较研究了将分子力场应用于沥青组分分子的结构参数(如键长、键角)和电荷参数与理论结果的偏差,以验证分子模拟力场对沥青分子体系的适应性和准确性。研究结果显示,分子结构参数与量子计算结果的偏差主要来自于对杂原子基团的电负性和共轭效应的描述,整体上偏差较小。3种力场对沥青分子体系研究均具有一定的适应性,其中,在键长、电荷方面的参数与量子力学计算结果较为接近。就沥青体系的键长、键角2种分子结构参数的分配而言,UFF力场综合表现略好,COMPASSⅡ力场次之;就电荷参数的分配而言,COMPASSⅡ力场准确性略高,UFF力场次之,Dreiding力场略低。总体而言,COMPASSⅡ力场及UFF力场对沥青分子体系研究的适应性及准确性更高。

Molecular simulation techniques have been widely applied in the microscopic mechanism research of asphalt,but the molecular structure theory and force field suitable for asphalt have not yet been established.The deviations of structural parameters(such as bond lengths and bond angles)and charge parameters of asphalt component molecules from quantum mechanics calculation results were compared by applying molecular force fields to verify the adaptability and accuracy of molecular simulation force fields to the asphalt molecular system.The results show that the deviations in molecular structural parameters from quantum calculation results are mainly attributed to the descriptions of electronegativity and conjugate effects of heteroatomic groups,and the overall discrepancies are small.Three force fields have a certain adaptability to the study of the asphalt molecular system.Among them,the parameters of bond lengths and charges are closer to the quantum mechanics calculation results.Regarding the distribution of the three molecular structural parameters of bond lengths and bond angles,the UFF force field has a slightly better overall performance,followed by the COMPASSⅡforce field.As for the distribution of charge parameters,the COMPASSⅡforce field has slightly higher accuracy,followed by the UFF force field,and the Dreiding force field is slightly lower.Overall,the COMPASSⅡforce field and UFF force field have higher adaptability and accuracy for the study of the asphalt molecular system.