Coincidence between Bond Strength, Atomic Abundance, and the Composition of Rocky Materials

Abstract

After removal the geologically and astrophysically underabundant Be, B, and F atoms from consideration, the strongest X−Y bonds in H n X−YH m hydrides are for O bonding with Al, Si, and Mg. These are stronger than the C−C bond in ethane or the C−O bond in methanol, for instance. These atoms, along with Fe, which is not a part of this study, are the dominant elements of rocky bodies and also happen to be the most common elements in the Earth's lithosphere. This study has examined the bond strengths of all H n X−YH m hydrides from Li to Cl, except the noble gas Ne. Hence, this work indicates a possible link between simple hydrides, like HOAlH 2 , and the beginning stages of mineral nanocrystal formation in the early solar system or interstellar grain nucleation. These strong bonds likely arise from notably strong ionic interactions between the third-row atoms with oxygen and may drive the early condensation of refractory materials in astrophysical contexts.

Pathways to Detection of Strongly-Bound Inorganic Species: The Vibrational and Rotational Spectral Data of AlH2OH, HMgOH, AlH2NH2, and HMgNH2

“…The constrained optimization has the maximum at 4.4 kcal/mol further implying the largely unhindered motion of the hydroxyl group even without the enlargement of ∠(H 1 -O-Al). Even so, this Al-O bond is notably stronger than any C−C or C−O single bond (Doerksen and Fortenberry, 2020). In spite of this nearly free rotation, the motion does not plague as deeply the anharmonic vibrational frequencies for AlH 2 OH as those reported for OAlOH (Fortenberry et al, 2020) likely due to the slightly deeper energy well and since the 424.1 cm −1 anharmonic frequency for AlH 2 OH ] 9 would require at least three quanta to excite above the barrier.…”

“…The B eff for HMgNH 2 is 11,213.43 MHz putting it in between that of the known inorganic, interstellar MgCN and SiO molecules. The Mg−N bond is relatively long at more than 1.9 Å, which makes sense in light of the fact that Al and O create stronger bonds than either Mg or N, much less a Mg−N bond, in these types of polarized covalent interactions (Doerksen and Fortenberry, 2020).…”

“…Recent work has shown that the strongest bonds between atoms on the first three rows of the periodic table (i.e. a majority of the most common elements in the Universe) are between one part oxygen and another part from one of aluminum, silicon, and magnesium, respectively (Doerksen and Fortenberry, 2020). Granted, this is after the astrophysically-depleted Be, B, and F atoms are discounted.…”

“…The present work utilizes similar quantum chemical computations as employed previously for OAlOH and AlOH (Fortenberry et al, 2020) to produce molecular structures, energies, and spectroscopic data for the four molecules at the nexus of strongly bound and containing highly abundant atoms as determined in earlier work (Doerksen and Fortenberry, 2020): AlH 2 OH, HMgOH, AlH 2 NH 2 , and HMgNH 2 . Additionally, these structures are known to challenge conventional thinking in that AlH 2 OH is planar, HMgOH is linear, and the two N-containing species are C 2v structures (Alabugin et al, 2014;Fugel et al, 2018;Sheridan and Ziurys, 2000;Xin et al, 2000;Grotjahn et al, 2001;Burton et al, 2019).…”

“…Additionally, these structures are known to challenge conventional thinking in that AlH 2 OH is planar, HMgOH is linear, and the two N-containing species are C 2v structures (Alabugin et al, 2014;Fugel et al, 2018;Sheridan and Ziurys, 2000;Xin et al, 2000;Grotjahn et al, 2001;Burton et al, 2019). This is most succinctly described as resulting from exceptionally strong yet floppy polarized covalent bonding between the two heavy atoms (Doerksen and Fortenberry, 2020;Fortenberry et al, 2020). In any case, their spectral features will be computed via quartic force fields (QFFs) which are fourth-order Taylor series expansions of the internuclear Hamiltonian.…”