Temperature dependent size effects on crystal growth of nanorods revealed by molecular dynamics simulations

RS Wang and FF Wang and GJ Yang and MX Wang and LT Kong and JF Li, JOURNAL OF APPLIED PHYSICS, 129, 194302 (2021).

DOI: 10.1063/5.0048957

Nano metallic materials are promising candidates in many engineering applications, whereas their thermal stability is generally of great concern. In this study, molecular dynamics simulations were performed to study the crystal growth process of CuZr nanorods with different diameters. An appreciable size effect was observed in the crystal growth rates. However, the trend of size dependence could be reversed by changing the temperature. For temperatures above 925 K, nanorods of smaller diameters grow slower than those with larger diameters, while for temperatures below 925 K, smaller nanorods grow faster. It turns out that the temperature dependent size effect originates from the competition between the thermodynamic and kinetic factors. Atoms in the surficial region of the nanorods have higher mobility while lower thermodynamic driving force for growth than those in the interior. Under different temperatures, the overwhelming factor varies, leading to the temperature dependent size effect. A phenomenological model was proposed accordingly to describe the size dependence, which is found to work well under all temperatures explored.

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