Development of the ReaxFF reactive force field for describing transition metal catalyzed reactions, with application to the initial stages of the catalytic formation of carbon nanotubes
Development of the ReaxFF reactive force field for describing transition metal catalyzed reactions, with application to the initial stages of the catalytic formation of carbon nanotubes
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DOI：
10.1021/jp046244d
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发表时间：
2005-01-27
影响因子：
2.9
通讯作者：
Goddard, WA
中科院分区：
文献类型：
--
作者：
Nielson, KD;van Duin, ACT;Goddard, WA
为了开发一种计算成本低廉的方法来模拟过渡金属催化反应的高温反应动力学，我们开发了一个ReaxFF反应力场，其中参数拟合到大量的量子力学（QM）训练集，包含相关反应的完整反应途径。在本文中，我们应用这种方法涉及碳材料加上钴，镍，铜原子的反应。我们发现，ReaxFF再现QM反应数据具有良好的准确性，同时也再现了钴，镍，铜原子的碳氢化合物碎片的结合特性。为了证明ReaxFF的适用性，我们进行了高温（1500 K）分子动力学模拟的非支化的全碳原料中存在和不存在的Co，Ni和Cu原子。我们发现，钴和镍的存在导致大量的支链碳原子，最终导致形成碳纳米管样物种。相比之下，我们发现，在相同的模拟条件下，铜导致非常少的支化，并导致产品没有纳米管的字符。在不存在金属的情况下，根本没有观察到支化。这些结果表明，镍和钴催化生产的纳米管样的物种，而铜不。这与实验观察结果非常一致，表明ReaxFF可以为研究过渡金属催化化学的动力学提供有用的计算工具。
With the aim of developing a computationally inexpensive method for modeling the high-temperature reaction dynamics of transition metal catalyzed reactions we have developed a ReaxFF reactive force field in which the parameters are fitted to a substantial quantum mechanics (QM) training set, containing full reaction pathways for relevant reactions. In this paper we apply this approach to reactions involving carbon materials plus Co, Ni, and Cu atoms. We find that ReaxFF reproduces the QM reaction data with good accuracy while also reproducing the binding characteristics of Co, Ni, and Cu atoms to hydrocarbon fragments. To demonstrate the applicability of ReaxFF we performed high-temperature (1500 K) molecular dynamics simulations on a nonbranched all-carbon feedstock in the presence and absence of Co, Ni, and Cu atoms. We find that the presence of Co and Ni leads to substantial amounts of branched carbon atoms, leading eventually to the formation of carbon-nanotube-like species. In contrast, we find that under the same simulation conditions Cu leads to very little branching and leads to products with no nanotube character. In the absence of metals no branching is observed at all. These results suggest that Ni and Co catalyze the production of nanotube-like species whereas Cu does not. This is in excellent agreement with experimental observations, demonstrating that ReaxFF can provide a useful and computational tractable tool for studying the dynamics of transition metal catalytic chemistry.