From DFT to Mass Spectrum: Understanding the Impact of Hydrogen on Evaporation Field in Atom Probe Tomography

The abstract is: Atom Probe Tomography (APT) provides powerful 3D atomic-scale characterization; however, data interpretation relies on simplified models that ignore local surface phenomena and field variations. This work addresses this limitation by using Density Functional Theory (DFT) to decode APT data, focusing on hydrogen (H) in metallic matrices. Beyond producing detectable molecular ions, H modifies evaporation pathways and alters responses to experimental parameters. Furthermore, its ubiquity in vacuum systems complicates distinguishing bulk from chamber-derived signals. Using aluminium (Al) as a benchmark, our ab initio calculations reveal how local H presence alters surface evaporation fields, energy barriers and modifies local bonding environments, enabling the prediction of complex evaporation probabilities and synthetic mass spectra. These insights demonstrate that mobile impurities can both enhance and delay evaporation while modifying field-barrier dependencies, providing a robust foundation for generalization beyond the Al-H system. Ultimately, this theory-guided approach paves the way for quantitative, high-fidelity APT characterization.