Creation of an Fe$_3$P Schreibersite Density Functional Tight Binding Model for Astrobiological Simulations

TL;DR

This paper develops a computationally efficient DFTB model for Fe3P schreibersite, enabling large-scale simulations of its chemical behavior relevant to prebiotic chemistry.

Contribution

A new semi-empirical DFTB model for Fe3P schreibersite that accurately captures its properties and is transferable to related iron phosphide and metal phases.

Findings

Model accurately reproduces bulk and surface properties of schreibersite.

Demonstrates transferability to other iron phosphide and metal allotropes.

Enables longer time and length scale simulations of schreibersite chemistry.

Abstract

The mineral schreibersite, e.g., Fe$_3$P, is commonly found in iron-rich meteorites and could have served as an abiotic phosphorus source for prebiotic chemistry. However, atomistic calculations of its degradation chemistry generally require quantum simulation approaches, which can be too computationally cumbersome to study sufficient time and length scales for this process. In this regard, we have created a computationally efficient semi-empirical quantum Density Functional Tight Binding (DFTB) model for iron and phosphorus-containing materials by adopting an existing semi-automated workflow that represents many-body interactions by linear combinations of Chebyshev polynomials. We have utilized a relatively small training set to optimize a DFTB model that is accurate for schreibersite physical and chemical properties, including its bulk properties, surface energies, and water absorption. We then show that our model shows strong transferability to several iron phosphide solids as well as multiple allotropes of iron metal. Our resulting DFTB parameterization will allow us to interrogate schreibersite aqueous decomposition at longer time and length scales than standard quantum approaches, allowing for investigations of its role in prebiotic chemistry on early Earth.