Ab Initio Computational Study on Fe₂NiP Schreibersite: Bulk and Surface Characterization

Abstract

Phosphorous is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorous is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms. A possible source of phosphorous is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphites. These materials, by simple interaction with water, produce oxygenated phosphorous compounds, which can easily react with organic molecules, thus forming C-O-P bonds. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on metallic Fe 2 NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material. The aim is to study the relative stability among different surfaces, to characterize both the nanocrystal morphology and the reactivity towards water molecules. File list (2) download file view on ChemRxiv schreibersite-paper_preprint.pdf (1.78 MiB) download file view on ChemRxiv schreibersite_paper_preprint_esi.pdf (724.96 KiB)

Systems Astrochemistry: A New Doctrine for Experimental Studies

“…In laboratory investigations of the chemistry occurring within interstellar ices, however, ices are usually deposited onto flat surfaces used for transmission or reflection spectroscopy (e.g., gold, zinc selenide, magnesium fluoride, etc.). Although previous studies have acknowledged that adsorbent morphology may play an important role in the chemistry or spectroscopy of the adsorbate ice (Perets et al, 2007;Gull et al, 2015;Qasim et al, 2017;Wakelam et al, 2017;Pantaleone et al, 2021), there is a scarcity of studies that have considered this experimentally, and fewer still that have considered the chemical influence of the interaction of flat substrates with incident radiation. One study by Mason et al (2008) showed that the infrared spectrum of hexagonal crystalline water ice deposited over soot particles suspended in an ultrasonic trap differed somewhat to that of the same ice deposited onto flat fluoride substrates traditionally used in laboratory astrochemistry.…”

Water Interaction with Fe2NiP Schreibersite (110) Surface: a Quantum Mechanical Atomistic Perspective

“…To study the weathering process of schreibersite, the interaction of water was only modeled on the (110) most stable schreibersite surface, as characterized in our recent work. 23 The adsorption of water was simulated at different surface coverage regimes, from a single water molecule to the monolayer up to a thin liquid water multilayer.…”

“…This setup was chosen according to the best results obtained in our previous work on the bulk and bare surfaces of schreibersite. 23 On O and H atoms, the original D* parameters were used. This method of choice is referred to as PBE-D*0 along the work.…”

Water Interaction with Fe2NiP Schreibersite (110) Surface: a Quantum Mechanical Atomistic Perspective

“…The same approach was used to characterize the pristine schreibersite. 23 Geometry optimizations and frequency calculations were performed with the gradient corrected PBE functional, 32 with a posteriori Grimme D2 correction, 33 modified for solids (D*). 34 Moreover, C6 atomic coefficients related to polarizabilities on Fe and Ni metal atoms were set to 0 (i.e.…”

“…[20][21][22] A recent computational work on the bulk and surface structures and properties of schreibersite was published by us. 23 According to that, it is unlikely that the oxygen of H2O (partially negatively charged) interacts with the surface P atoms, which also bring a partial (close to -1e) negative charge, [23][24][25][26] thus resulting in an electrostatic repulsion. In the present paper we simulate the adsorption of water on the most stable facet of schreibersite, namely the {110} exploring different water's coverage regimes, up to a water multilayer.…”