  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).
