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负载的纳米金属具有更好的催化活性,但其制备过程中容易发生团簇烧结现象。为尽量避免这一现象发生,纳米金属团簇的熔化及烧结作用需加以仔细研究。本工作利用MS软件、COMPASS力场以及软件自有分析手段,对截取粒径在(1.6~3)nm范围的5种纳米镍团簇的熔化性质及结构演变进行了模拟计算。结果表明,可采用定向相关函数、系统的能量以及径向分布函数曲线3种手段来联合指示团簇的熔化区间,其中定向相关函数指示最为清晰。对尺寸效应的模拟结果显示,当粒径超过2 nm时,纳米镍团簇存在预熔化现象,这与已有的研究结果相一致;纳米镍的完全熔化温度区间随粒径的增加而升高,但均低于块状镍的熔点,这一结果与大多数的研究结果相一致。本文的研究结果将为进一步研究纳米镍的烧结提供一定的方法和理论支撑。
The supported nano-metal has better catalytic activity, but the phenomenon of cluster sintering is easy to occur in the preparation process. To avoid this phenomenon, the melting and sintering of nano-metal clusters need to be carefully studied. In this work, the melting properties and structure evolution of five nano-nickel clusters with particle size in the range of (1.6 ~ 3) nm were simulated by using MS software, COMPASS force field and software’s own analysis method. The results show that the directional correlation function, the energy of the system and the radial distribution function curve can be used to jointly indicate the melting range of the clusters, of which the directional correlation function indicates the most clearly. The simulation results on the size effect show that when the particle size exceeds 2 nm, the pre-melting of the nano-nickel clusters exists, which is consistent with the existing research results. The full melting temperature range of the nano-nickel increases with the increase of the particle size , But lower than the melting point of bulk nickel, a result consistent with most of the findings. The results of this paper will provide some methods and theoretical support for the further study of the sintering of nano-nickel.