Enstatite (MgSiO3) and forsterite (Mg2SiO4) monomers and dimers: highly detectable infrared and radioastronomical molecular building blocks

Abstract

ABSTRACT Isolated MgSiO3 and Mg2SiO4 molecules are shown here to exhibit bright infrared (IR) features that fall close to unattributed astronomical lines observed toward objects known to possess crystalline enstatite and forsterite, minerals of the same respective empirical formulae. These molecules are therefore tantalizing candidates for explaining the origin of such features. Furthermore, the C2v monomer minima of each formula set have dipole moments on the order of 10.0 D or larger making them desirable candidates for radioastronomical observation as enabled through rotational spectroscopic data further provided in this high-level CCSD(T)-F12/cc-pVTZ-F12 quantum chemical study. Astrophysical detection of these molecules could inform the build-up pathways for creating nanocrystals from small molecules in protoplanetary discs or could show the opposite in explaining the destruction of enstatite and forsterite minerals in supernovae events or other high-energy stellar processes. This work also shows that the lowest energy isomers for molecules containing the geologically necessary elements Mg and Si have oxygen bonded between any of the other heavier elements making oxygen the glue for pre-mineralogic chemistry.