  In atom probe tomography (APT), atoms from the surface of a needle shape
specimen are evaporated under a high electric field and analyzed via time of
flight mass spectrometry and position sensitive detection. 3D reconstruction of
the atom positions follows a simple projection law, which can sometimes lead to
artifacts due to deviation from an assumed ideal evaporation sequence. Here, we
revisit the evaporation behavior of [001]-oriented $\gamma$-TiAl using a
full-dynamics simulation approach empowered by molecular dynamics. Without any
knowledge of charge states or assumptions about evaporation fields, we
successfully reproduced the lack of distinct Al and Ti layers observed in
reconstructions of experimental data which is traditionally attributed to the
retention of Al on the evaporating surface. We further showed that a step-wise
bond breaking process of Ti in contrast to the simultaneous bond breaking of Al
explains the seemingly counterintuitive preferential evaporation of the
strongly bonded Ti atoms.
