Theoretical modelling of the adsorption of neutral and charged sulphur-bearing species on to olivine nanoclusters

• DOI: 10.1093/mnras/stad3896
• Publication Date: 2023-12-20T06:32:30Z
• Authors: Jessica Perrero; Leire Beitia-Antero; Asunción Fuente; Piero Ugliengo; Albert Rimola
• Keywords: Nanoclusters; Chemisorption

Sulphur depletion in the interstellar medium (ISM) is a long-standing issue, as only 1% of its cosmic abundance detected dense molecular clouds (MCs), while it does not appear to be depleted other environments. In addition gas phase species, MCs also contain dust grains, which are irregular, micron-sized, solid aggregates carbonaceous materials and/or silicates. Grains provide surface where species can meet, accrete, and react. Although freeze-out sulphur onto grains could explain depletion, OCS and, tentatively, SO$_2$ were observed on their surfaces. Therefore, our aim investigate interaction between sulphur-containing exposed mineral core at stage prior when observed. Here, grain represented by olivine nanoclusters, one most abundant minerals ISM, with composition Mg$_4$Si$_2$O$_8$ Mg$_3$FeSi$_2$O$_8$. We performed series quantum mechanical calculations characterize adsorption 9 S-bearing both neutral charged, nanoclusters. Our reveal that Fe-S preferred Mg-S, causing sometimes chemisorption adsorbate. These more strongly adsorbed bare silicate cores than water ice mantles, hence therefore likely sticking forming part core. This demonstrates cloud envelopes determine S-depletion clouds.