ABSTRACT In this paper, we have extended our previous study of the static and dynamic properties (self-diffusion coefficient Dself and friction coefficient ζ) of liquid n-alkane systems up C400 at several temperatures (∼2300 K) using molecular dynamics (MD) simulations in the canonical ensembles. For the small n-alkanes with n ≤ 120 (n: the chain length), the chains are clearly ⟨R2 ee⟩/6⟨R2 g⟩ ≥ 1 (1.06 ∼ 1.44), which leads to the conclusion that the liquid n-alkanes are far away from the ideal chain regime. But for the n-alkanes of n ≥ 160, the chains are ⟨R2 ee⟩/6⟨R2 g⟩ ≈ 1, indicating that they are Gaussian. It is found that the long chains of these n-alkanes at high temperatures show abnormalities in density and friction coefficient. We observed a clear transition in the power law dependence of n-alkane self-diffusion coefficient on the molecular weight (M) of n-alkane, Dself ∼ M−γ, occurs in the range C120∼C160 at temperatures of 318, and 618 K, corresponding to a crossover from the ‘oligomer’ to the ‘Rouse’ regime. The entanglement lengths (Ne) are calculated by the Z1 code and discussed shortly.

中文翻译：

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C12∼C400中型液态正烷烃的静态和动态特性：分子动力学模拟研究

摘要在本文中，我们使用分子动力学 (MD) 扩展了我们之前对 C400 以上液体正烷烃系统在几个温度 (~2300 K) 下的静态和动态特性（自扩散系数 Dself 和摩擦系数 ζ）的研究规范集成中的模拟。对于 n ≤ 120（n：链长）的小正构烷烃，链显然是 ⟨R2 ee⟩/6⟨R2 g⟩ ≥ 1 (1.06 ∼ 1.44)，由此得出结论：液体 n-烷烃与理想的链体系相去甚远。但是对于n≥160的n-烷烃，链是⟨R2 ee⟩/6⟨R2 g⟩≈1，表明它们是高斯​​的。发现这些正构烷烃的长链在高温下表现出密度和摩擦系数异常。我们观察到正构烷烃自扩散系数对正构烷烃分子量 (M) 的幂律依赖性的明显转变，Dself ∼ M−γ，在 318 和 618 的温度下发生在 C120∼C160 范围内K，对应于从“低聚物”到“Rouse”机制的交叉。纠缠长度 (Ne) 由 Z1 代码计算并稍后讨论。