Joshi Nikhil P, Spearot Douglas E, Bhat Deepak
Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701, USA.
J Nanosci Nanotechnol. 2010 Sep;10(9):5587-93. doi: 10.1166/jnn.2010.2457.
Molecular dynamics simulations with many-body interatomic potentials are used to study melting of Ni and Fe nanoparticles with diameters that range between 2 and 12 nm. Two different embedded-atom method interatomic potentials are used for each element. The capability of each interatomic potential to model (i) size-dependent melting in nanoparticles and (ii) the bulk melting temperature of Ni or Fe is explored. In agreement with existing theory, molecular dynamics simulations show that the melting temperature of non-supported nanoparticles decreases with decreasing nanoparticle size, displaying a linear relationship with the inverse of nanoparticle diameter. However, molecular dynamics simulations using the interatomic potentials considered in this work provide a lower estimate than existing theory for the sensitivity of the melting temperature to nanoparticle size (slope of linear relationship). Molecular dynamics simulations demonstrate that melting is surface initiated and that a finite temperature range exists in which partial melting of the nanoparticle occurs. This observation is very important in the development of advanced vapor-liquid-solid models for catalyst-assisted single-walled carbon nanotube synthesis.
利用具有多体原子间势的分子动力学模拟来研究直径在2至12纳米之间的镍和铁纳米颗粒的熔化过程。每种元素使用两种不同的嵌入原子方法原子间势。探讨了每种原子间势对（i）纳米颗粒中尺寸依赖性熔化以及（ii）镍或铁的体相熔化温度进行建模的能力。与现有理论一致，分子动力学模拟表明，无支撑纳米颗粒的熔化温度随纳米颗粒尺寸减小而降低，与纳米颗粒直径的倒数呈线性关系。然而，使用本工作中所考虑的原子间势进行的分子动力学模拟，对于熔化温度对纳米颗粒尺寸的敏感性（线性关系的斜率），所提供的估计值比现有理论要低。分子动力学模拟表明，熔化是从表面开始的，并且存在一个有限的温度范围，在此范围内纳米颗粒会发生部分熔化。这一观察结果在用于催化剂辅助单壁碳纳米管合成的先进气-液-固模型的开发中非常重要。
