Accurate meso-scale dynamics by kinetic Monte Carlo simulation via free energy multicanonical sampling: oxygen vacancy diffusion in BaTiO3
Accurate meso-scale dynamics by kinetic Monte Carlo simulation via free energy multicanonical sampling: oxygen vacancy diffusion in BaTiO3
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DOI：
10.1080/27660400.2021.1930915
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发表时间：
2021-01
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影响因子：
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通讯作者：
H. Nakata;M. Araidai;S. Bai;H. Hirano;T. Tada
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作者：
H. Nakata;M. Araidai;S. Bai;H. Hirano;T. Tada
摘要提出了一种概念上精确的方法，将自由能多重正则采样与中尺度动力学蒙特卡罗（kMC）动力学联系起来。kMC模拟所需的输入参数是每个事件的尝试频率和活化能，并且自由能多规范采样使得能够获得作为温度的函数的动力学参数，这是与基于固定尝试频率和活化能的常规kMC方法的最显著差异。将本方法应用于包含Zn掺杂剂（160 ppm）的单晶BaTiO 3中的氧扩散，其中通过实验确认了氧扩散的异常;氧扩散系数在1080 K附近略微下降。我们在1020 ~ 1120 K温度范围内进行了1 μs kMC动力学计算，得到了在1060 K附近的扩散异常，这是常规kMC计算所不能得到的。此外，用本方法计算的扩散系数与实验值在同一数量级，而用常规方法计算的扩散系数比实验值至少大一个数量级。结果表明，与传统的方法相比，本方法的优点，因为任何假设和固定的动力学参数是不需要在动力学模拟。
ABSTRACT A conceptually accurate method to connect the free energy multicanonical sampling to meso-scale kinetic Monte Carlo (kMC) dynamics is proposed. The required input parameters for kMC simulation are the attempt frequency and activation energy for each event, and the free energy multicanonical sampling enables to obtain the kinetic parameters as a function of temperature, which is the most significant difference from a conventional kMC approach that is based on fixed attempt frequency and activation energy. The present approach is applied to oxygen diffusion in single crystal BaTiO3 including Zn dopant (160 ppm) where an anomaly in the oxygen diffusion is experimentally confirmed; the oxygen diffusion coefficient is slightly dropped at around 1080 K. We carried out 1 μs kMC dynamics in the temperature range of 1020 to 1120 K, and obtained a diffusion anomaly at around 1060 K, which is not obtained in conventional kMC calculations. In addition, the calculated diffusion coefficients using the present approach are in the same order as those of experimental ones, whereas the calculated diffusion coefficients using the conventional method are larger than those of experiment by one order of magnitude at least. The results indicate the advantages of the present approach in comparison with the conventional ones because any assumption and fixation of kinetic parameters are not required in the dynamics simulation.