Yonetani Yoshiteru
CREST-JST, Japan Atomic Energy Agency, 8-1 Umemidai, Kizu-cho, Soraku-gun, Kyoto 619-0215, Japan.
J Chem Phys. 2006 May 28;124(20):204501. doi: 10.1063/1.2198208.
Cutoff treatment is the simplest approach for evaluating intermolecular interactions in molecular dynamics simulations. It has been believed that increasing cutoff length makes simulation results better. On the contrary, our results of the bulk water simulations studied within the range of cutoff lengths, 9-18 A, showed an opposite tendency: the artifact was enhanced by increasing the cutoff length. Especially, in terms of the distance dependent Kirkwood factor GK(r), it was clearly shown that the orientational behavior of water molecules becomes gradually worse as the cutoff length becomes longer. The artifact enhanced by the increased cutoff length led to a reported spurious artifact, i.e., phase transition [Y. Yonetani, Chem. Phys. Lett. 406, 49 (2005)]. Though the cutoff artifact was largely reduced by adopting a force switching technique, it did not completely remove the anomalous cutoff length dependence of the artifact. These results suggest that increasing the cutoff should not be attempted regardless of whether the switching force is adopted or not.
截断处理是分子动力学模拟中评估分子间相互作用的最简单方法。人们一直认为增加截断长度会使模拟结果更好。相反，我们在9 - 18埃的截断长度范围内对体相水进行模拟的结果显示出相反的趋势：随着截断长度的增加，假象增强。特别是，就距离相关的柯克伍德因子GK(r)而言，很明显随着截断长度变长，水分子的取向行为逐渐变差。截断长度增加导致的假象会引发一种已报道的虚假假象，即相变[米谷洋，《化学物理快报》406, 49 (2005)]。尽管采用力切换技术可大大减少截断假象，但它并未完全消除假象对截断长度的异常依赖性。这些结果表明，无论是否采用切换力，都不应尝试增加截断长度。
