Under InterCat, we will develop and use modern Machine Learning (ML) based regression methods to speed up the computational description of nanoparticle models for carbonaceous and silicate dust grains. The methods will further include evolutionary algorithm (EA) based approaches to provide a sampling of high formation energy structures. The approach taken will encompass fitting of force fields and establishment of surrogate energy landscapes for the particles, which will allow for a statistically sound sampling of amorphous states of nanoscale dust grains and for conducting kinetic nucleation and growth simulations. The dust grain distribution will be analyzed using ML-based clustering methods and categorized according to i) calculated IR spectral features for direct comparison with observations to identify structures of interstellar relevance and ii) the local environments around each chemical element constituting the possible reactive sites on the surfaces of interstellar dust particles. Resulting structures will be compared to observation-based models of interstellar dust and to novel measurements on the carbonaceous dust component from JWST.
We will synthesize realistic dust grain analogues exhibiting a preponderance of specific reactive sites. Examples are PAH or graphene coated silicate and SiC nanoparticles28 and carbonaceous nanograins with varying degrees of aromatic and aliphatic content synthesized via chemical vapor deposition (CVD) or from deposition of carbon atoms or PAH molecules using atomic and molecular beam techniques. Nanostructured amorphous silicate surfaces and silicate nanoparticles with tunable crystallinity will be directly synthesized on surfaces. Functional groups, ad-atoms: O, H, N, C and very active metal (e.g. Fe or Mg ) single-atom catalysts and molecular adsorbates and layers, can then be added to these systems. Synthesized model surfaces will be characterized by Scanning Probe Microscopy (STM and AFM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Transmission Electron Microscopy at AU.