XPS spectra of atmospheric aerosols: A combined DFT and ML approach

: Adhyatma, Abdurrahman; Das, Mandira; Lin, Jack; Prisle, Nønne; Todorović, Milica

: Recent Advances in Computer-aided X-ray Spectroscopy

: 2024

Aerosols, ranging from nano to micro-sized air-suspended particles, are key players in transmitting pathogens and regulating Earth's climate. The surface of aerosol critically determines their interaction with atmospheric water and other gas-phase compounds, affecting their physical and chemical properties. The aerosol surface responds uniquely to different atmospheric compounds, resulting in unknown surface structures at the vapor/particle interface. However, despite advances in high-tech instruments, fully identifying the atomic surface structure of the interface remains challenging. In this work, we address this challenge by exploring the atomic structure of aerosol and atmospheric compounds’ interface using the Density Functional Theory in conjunction with active learning methods.

Sodium Chloride (NaCl) stands out as the most abundant aerosol particle. The interaction of NaCl surface with atmospheric water is a prototype as a starting point of this study. We systematically modeled the water molecule adsorption on the NaCl 001 surface. The simulated X-ray Photoelectron Spectroscopy (XPS) reveals the surface structure arrangement of the interface. We compare our theoretical XPS spectra of clean NaCl 001 surface and water absorbed NaCl surface with the experiment by Lin et. al [1].