Simulating Electron Beam – Materials Interactions with Real-Time Electron Dynamics

Time-dependent electron dynamics is used to model interaction of electron beam with materials for beam energy and positions relevant to scanning transmission electron microscopy. We investigate the real-time and linear response framework for simulating the response of small molecular systems including benzene and pyrene. The position dependence of selection rules for electron beam induced electronic excitaitons is discussed Higher order terms in the multipolar expansion of the electrostatic potential are shown to contribute significantly to the energy loss probability except in the high impact parameter regime where the electric fields emanated by the electron beam are essentially homogeneous over the volume of the material. Results of this study have implications for the prediction of electron energy loss spectra from first principles, and can lead to a more complete understanding of mechanisms underlying both directed nanoscaled materials manipulations and accidental radiation damage sustained by materials subjected to electron beams with energies below the material’s knock-on threshold.