New molecular species of potential interest to interstellar chemistry: A theoretical study of MgSiN, MgNSi and related species

An ab initio study has been performed to characterize the probable magnesium containing interstellar species MgSiN, MgNSi and their ionized, hydrogenated and protonated forms. We are able to locate four protonated and four hydrogenated magnesium species with planar geometry at MP2(Full)/cc-pVTZ level of theory. MgNSi is found to be more stable than MgSiN and their connecting transition state is also located. The ionization potential for both MgSiN and MgNSi are small, 7.91 eV and 7.01 eV, respectively. All possible protonation sites are considered for these two species but the preferred protonation sites are found to be silicon for MgNSi and nitrogen for MgSiN. Enthalpies of formation at 0 K (ΔfH°) and bond dissociation energies (Do(X-Y)) are computed for all the species at G3 and G3MP2 level of theory. Finally, the reaction enthalpies for ion-molecule processes are calculated and most of the processes are found to be exothermic and hence thermodynamically favorable in interstellar region.