PowerMEIS 3: A versatile tool for simulating ion and electron scattering

The aggressive roadmap for nanotechnology is driving the development of characterization techniques capable of providing nanometric resolution while preserving structural and chemical information for increasingly complex samples. Ion and electron scattering have emerged as powerful methodologies to meet these demands. However, due to the sophistication of modern samples, data interpretation heavily relies on advanced simulations. In this context, we have developed the PowerMEIS 3 computer program, a versatile Monte Carlo tool for simulating the scattering spectra of ions and electrons. This program has been rewritten from its previous versions and incorporates several new features. A detailed description of its implementation is provided after introducing the necessary physical principles. The program's wide range of applications is illustrated through several examples, including Medium Energy Ion Scattering, Rutherford Backscattering Spectrometry , molecular ion scattering, Nuclear Reaction Profiling, and Reflection Electron Energy Loss Spectroscopy. In particular, we demonstrate three distinct strategies for calculating the path integral: the Single Scattering, Connected Trajectory , and Direct Trajectory approaches, all based on a voxel representation of the target sample. Additionally, we compare the performance of PowerMEIS 3 program to other established programs, such as TRBS and SIMNRA . The Connected Trajectory approach is a novel feature in scattering simulations and significantly reduces the simulation time for Multiple Scattering calculations. Moreover, it enables simulations of nanostructures at any incidence angle, a capability not supported by other programs. The program also offers the option to run simulations remotely on a server hosted at Universidade Federal do Rio Grande do Sul (UFRGS). Finally, we discuss the limitations of the Connected Trajectory approach at lower energies, primarily due to the time reversal approximation employed, and highlight possibilities for further development.