Efficient and versatile model for vibrational STEM-EELS

TL;DR

This paper presents a new simulation method for vibrational STEM-EELS that combines molecular dynamics and multislice calculations, accurately modeling phonon-loss processes with computational efficiency.

Contribution

A novel simulation approach integrating a delta-thermostat with frozen phonon approximation for vibrational STEM-EELS.

Findings

Good agreement with experimental data for hBN

Accurate vibrational spectrum imaging

Comparable computational cost to standard methods

Abstract

We introduce a novel method for the simulation of the impact scattering in vibrational scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) simulations. The phonon-loss process is modeled by a combination of molecular dynamics and elastic multislice calculations within a modified frozen phonon approximation. The key idea is thereby to use a so-called $\delta$-thermostat in the classical molecular dynamics simulation to generate frequency dependent configurations of the vibrating specimen's atomic structure. The method includes correlated motion of atoms and provides vibrational spectrum images at the cost comparable to standard frozen phonon calculations. We demonstrate good agreement of our method with simulations and experiments for a 15nm flake of hexagonal boron-nitride (hBN).