Yeo Sang Chul, Lo Yu Chieh, Li Ju, Lee Hyuck Mo
Department of Materials Science and Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, South Korea.
Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Chem Phys. 2014 Oct 7;141(13):134108. doi: 10.1063/1.4896610.
Ammonia (NH3) nitridation on an Fe surface was studied by combining density functional theory (DFT) and kinetic Monte Carlo (kMC) calculations. A DFT calculation was performed to obtain the energy barriers (Eb) of the relevant elementary processes. The full mechanism of the exact reaction path was divided into five steps (adsorption, dissociation, surface migration, penetration, and diffusion) on an Fe (100) surface pre-covered with nitrogen. The energy barrier (Eb) depended on the N surface coverage. The DFT results were subsequently employed as a database for the kMC simulations. We then evaluated the NH3 nitridation rate on the N pre-covered Fe surface. To determine the conditions necessary for a rapid NH3 nitridation rate, the eight reaction events were considered in the kMC simulations: adsorption, desorption, dissociation, reverse dissociation, surface migration, penetration, reverse penetration, and diffusion. This study provides a real-time-scale simulation of NH3 nitridation influenced by nitrogen surface coverage that allowed us to theoretically determine a nitrogen coverage (0.56 ML) suitable for rapid NH3 nitridation. In this way, we were able to reveal the coverage dependence of the nitridation reaction using the combined DFT and kMC simulations.
通过结合密度泛函理论（DFT）和动力学蒙特卡罗（kMC）计算，研究了铁表面上的氨（NH₃）氮化作用。进行DFT计算以获得相关基本过程的能垒（Eb）。在预先覆盖有氮的Fe（100）表面上，精确反应路径的完整机制分为五个步骤（吸附、解离、表面迁移、渗透和扩散）。能垒（Eb）取决于氮的表面覆盖率。DFT结果随后被用作kMC模拟的数据库。然后，我们评估了在预先覆盖有氮的铁表面上的NH₃氮化速率。为了确定实现快速NH₃氮化速率所需的条件，在kMC模拟中考虑了八个反应事件：吸附、解吸、解离、逆向解离、表面迁移、渗透、逆向渗透和扩散。本研究提供了受氮表面覆盖率影响的NH₃氮化的实时尺度模拟，这使我们能够从理论上确定适合快速NH₃氮化的氮覆盖率（0.56 ML）。通过这种方式，我们能够使用DFT和kMC模拟相结合的方法揭示氮化反应对覆盖率的依赖性。
