科研之友
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摘要
Understanding the physical and chemical behavior of supported nanoscale catalysts is of fundamental and technological importance. However, their behavior remains poorly understood, in part due to their complex, dynamical structure and the nature of interactions at the nanoscale. We found previously that real-time ab initio finite temperature DFT simulations provide fundamental insights into the dynamic and electronic structure of nanopartides. Unfortunately, such first-principles calculations are very computationally intensive. To make such simulations more feasible, we have developed a hybrid version of the classical Sutton Chen model potential which is orders of magnitude more efficient. This potential is parametrized to previous DFT/MD simulations and accounts for many-body effects induced by the support. The model is applied to Pt-10,Pt-20 nanopartides supported on a model gamma-Al2O3 surface. In addition to the thermal variation of the internal structure, the model also predicts diffusion coefficients and bond-breaking rates. The simulations reveal size-dependent dynamical changes with increasing temperature, as the clusters go from a "frozen" state attached to the support, to a "liquid" state where they are free to diffuse. These changes provide a rationale for the observed negative thermal expansion. Implications for nanoscale catalysis are briefly discussed.
- 出版日期2016-7-14
