SAFARI – A low and hyperthermal energy ion scattering simulation

Abstract

SAFARI [1][2] is a classical molecular dynamics simulation designed to assist with analysis of low and hyperthermal energy ion spectra (1 eV - 1 keV) for ion-surface scattering experiments. SAFARI is optimized for this specific energy range to reduce the required runtime, and to produce more precise spectra. This paper discusses the algorithms used in SAFARI, as well as various optimizations implemented for the specific ranges involved. Program summaryProgram Title: SAFARICPC Library link to program files:https://doi.org/10.17632/t5kxgnmjwv.1Developer's repository link:https://github.com/SINS-Lab/SEA-SAFARICode Ocean capsule:https://codeocean.com/capsule/3787536Licensing provisions: MITProgramming language: C++Nature of problem: SAFARI models low and hyperthermal energy (1 eV - 1 keV) ion scattering spectra. This energy range requires molecular dynamics techniques to adequately reproduce experimental spectra, as the energies are too low for appropriate use of the sequential binary collision approximation. Several approximations and optimisations are used to reduce the runtime of the simulation, to allow generating larger statistical datasets.Solution method: SAFARI utilises a predictor-corrector integrator, and classical Hamiltonian mechanics to model the trajectory of the ions. Ion-lattice forces are computed by a combination of image parameters, optional frictional losses, and binary pair potentials. The pair potentials are only computed for nearby lattice sites to reduce the computational complexity of the simulation.