【作者】 余翔； 杨小震；

【Author】 Yu Xiang,Yang Xiaozhen~* (Beijing National Laboratory for Molecular Sciences,Joint Laboratory of Polymer Science and Materials,State Key Laboratory of Polymer Physics and Chemistry,Institute of Chemistry,Chinese Academy of Sciences, Beijing,100190)

【机构】 中国科学院化学研究所高分子物理和化学国家重点实验室；

【摘要】 在分子力学和分子动力学模拟中,计算分子中各原子上的电荷分布是一个十分重要的步骤,特别是在研究极性分子时,电荷分布的准确程度对于模拟结果有很大的影响。计算电荷分布有很多种方法,如Gasteiger方法、Qeq方法、量子力学半经验算法和从头计算法等,也有部分力场自带了电荷分布信息,如OPLS力场。这些方法的计算速度和所得结果的准确程度有较大的差别,Gasteiger方法的速度最快,但准确程度最低,从头计算法最为精确,但耗时也最长。Qeq方法和半经验算法的准确程度介于前两者之间,但在计算速度上,Qeq方法快于半经验算法。从综合的角度来看,在对拥有数百个至数千个原子的体系进行分子力学或分子动力学模拟时,Qeq方法是一种计算耗时和准确性较为平衡的算法,它的计算时间复杂度为T(n)=O(n~2)。本工作采用Qeq方法对含有450个原子的聚乙烯链进行了电荷分布的计算,将得到的结果与用Gaussian03(DFT,6-31G)计算得到的结果进行了对比。通过对比可以发现,两者计算得到的电荷分布整体趋势相同,并且Qeq方法得到的单个原子电荷的绝对值约为从头计算法所得结果的4倍,准确程度不及从头计算法,但比Gasteiger法精确得多。在计算时间方面,Qeq方法的计算速度约为从头计算法的30至50倍左右。因此,对于需要实时计算电荷分布的分子动力学模拟,Qeq方法是更为有效的方法。更多还原

【Abstract】 How to calculate the charge distribution for each atom in molecular mechanics simulation and molecular dynamics simulation is quite important especially for simulating polar molecules.There several methods to calculate the charge distribution such as Gasteiger,Qeq, semi-empirical and ab.initio methods.Among them,the Qeq method does best performance between the accuracy of results and the CPU time costs.In present work,the Qeq method was applied to calculate the charge distribution of a polyethylene chain which has about 450 atoms. And the results were compared with the results obtained by Gaussian 03.It can be found that the data from Qeq and ab.initio methods have the same trends however the former ones were about 4 times larger than later ones.So the Qeq method could not obtain accurate results as ab.initio method but were much more accurate than Gasteiger method.Meanwhile,the Qeq method can perform 30 to 50 times faster than ab.initio,as a result,Qeq method does have much higher value in molecular dynamics simulation when the charge distribution need to be recalculated step by step.更多还原