Mendis B G
Department of Physics, Durham University, South Road, Durham DH1 3LE, UK.
Microsc Microanal. 2023 Jun 9;29(3):1111-1123. doi: 10.1093/micmic/ozad052.
Multislice simulations of 4D scanning transmission electron microscopy (4D STEM) data are computationally demanding due to the large number of STEM probe positions that must be calculated. For accurate analysis, inelastic scattering from phonons and plasmons must also be included. However, current frozen phonon and Monte Carlo plasmon techniques require a separate calculation for each different phonon/plasmon configuration, and are therefore not suitable for scaling up to 4D STEM. Here a phase scrambling algorithm (PSA) is proposed, which treats all phonon/plasmon configurations simultaneously. A random phase is introduced to maintain incoherence between the different inelastic scattering events; this is the phase scrambling part of the algorithm. While for most applications, a few tens of frozen phonon iterations are sufficient for convergence, in the case of plasmon scattering as many as tens of thousands of iterations may be required. A PSA is statistically more representative of inelastic scattering, and achieves significant savings in computation time for plasmons. The increase in speed is a pre-requisite for 4D STEM inelastic scattering simulations.
由于必须计算大量的扫描透射电子显微镜（4D STEM）数据的多切片模拟，其计算量很大。为了进行准确的分析，还必须考虑声子和等离子体激元的非弹性散射。然而，当前的冻结声子和蒙特卡罗等离子体激元技术需要对每个不同的声子/等离子体激元配置进行单独计算，因此不适用于扩展到4D STEM。本文提出了一种相位加扰算法（PSA），该算法可同时处理所有声子/等离子体激元配置。引入随机相位以保持不同非弹性散射事件之间的不相干性；这是该算法的相位加扰部分。虽然对于大多数应用，几十次冻结声子迭代就足以收敛，但在等离子体激元散射的情况下，可能需要多达数万次迭代。PSA在统计上更能代表非弹性散射，并在等离子体激元的计算时间上实现了显著节省。速度的提高是4D STEM非弹性散射模拟的先决条件。
