Khodyrev V A, Andrzejewski R, Rivera A, Boerma D O, Prieto J E
Institute of Nuclear Physics, Moscow State University, Moscow 119899, Russia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 2):056707. doi: 10.1103/PhysRevE.83.056707. Epub 2011 May 16.
An efficient approach for the simulation of ion scattering from solids is proposed. For every encountered atom, we take multiple samples of its thermal displacements among those which result in scattering with high probability to finally reach the detector. As a result, the detector is illuminated by intensive "showers," where each event of detection must be weighted according to the actual probability of the atom displacement. The computational cost of such simulation is orders of magnitude lower than in the direct approach, and a comprehensive analysis of multiple and plural scattering effects becomes possible. We use this method for two purposes. First, the accuracy of the approximate approaches, developed mainly for ion-beam structural analysis, is verified. Second, the possibility to reproduce a wide class of experimental conditions is used to analyze some basic features of ion-solid collisions: the role of double violent collisions in low-energy ion scattering; the origin of the "surface peak" in scattering from amorphous samples; the low-energy tail in the energy spectra of scattered medium-energy ions due to plural scattering; and the degradation of blocking patterns in two-dimensional angular distributions with increasing depth of scattering. As an example of simulation for ions of MeV energies, we verify the time reversibility for channeling and blocking of 1-MeV protons in a W crystal. The possibilities of analysis that our approach offers may be very useful for various applications, in particular, for structural analysis with atomic resolution.
提出了一种用于模拟离子从固体散射的有效方法。对于每一个遇到的原子，我们在那些导致高概率散射最终到达探测器的热位移中取多个样本。结果，探测器被密集的“簇射”照亮，其中每次探测事件都必须根据原子位移的实际概率进行加权。这种模拟的计算成本比直接方法低几个数量级，并且对多次和多重散射效应进行全面分析成为可能。我们将此方法用于两个目的。首先，验证了主要为离子束结构分析而开发的近似方法的准确性。其次，利用重现广泛实验条件的可能性来分析离子 - 固体碰撞的一些基本特征：低能离子散射中双重剧烈碰撞的作用；非晶样品散射中“表面峰”的起源；多重散射导致的散射中能离子能谱的低能尾部；以及随着散射深度增加二维角分布中阻塞图案的退化。作为兆电子伏能量离子模拟的一个例子，我们验证了1兆电子伏质子在钨晶体中的沟道效应和阻塞效应的时间可逆性。我们的方法所提供的分析可能性对于各种应用可能非常有用，特别是对于原子分辨率的结构分析。
