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

Abstract

<p>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<sub>2</sub>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. </p>

First-principles surface characterization and water adsorption of Fe3P schreibersite

“…The remaining (001) and (111) surface energies indicate that the type 2 termination is lower in energy overall by ∼ 0.20 − 0.25 J/m 2 . These results show similar trends to previous 46 where DFT calculations also indicated that (110) facet is the most stable.…”

“…Both approaches yield a slightly more dense structure with respect to experiment, similar to previous results for nickel-containing schreibersite ((Fe 2 , Ni)P). 46 We have further validated our approach by computing the zero temperature cold curve up to 20 GPa, with comparison to experimental data. 44,45 We have also computed the bulk modulus by fitting our data with a second order Birch-Murnaghan 47,48 equation of state.…”

“…In order to improve computational efficiency, we have used the standard approach of fixing the positions of some non-surface atoms in order to replicate surface-bulk interactions. 38,46,51 In our case, we included a total of three active atomic layers between the top and the bottom surface of the slabs (i.e., roughly 1.5 atomic layers for each), while excluding the remaining atoms in the internal layers by freezing their degrees of freedom.…”