Electronic structure and charge ordering in magnetite: implications for the Fe₃O₄(001)–water interface

Abstract

Electronic structure calculations on atomistic models of magnetite (Fe 3 O 4 ) provide valuable insight into the structure and properties that dictate the behaviour of magnetite under environmental conditions. The charge ordering in the bulk oxide controls the reactivity of the exposed surfaces, but it has been difficult to measure experimentally or predict theoretically. We use spin-polarised density functional theory to calculate the structure of bulk Fe 3 O 4 and its (001) and (111) surface terminations. We then present an ab initio thermodynamics approach to determine the most energetically favourable clean and hydroxylated surface terminations of Fe 3 O 4 (001). We present results on molecular water adsorption and heterolytic dissociation at both quarter-and half-monolayer coverage for Fe 3 O 4 (001). Our calculations suggest that the tetrahedral (001) surface termination is the most energetically stable across all oxygen chemical potentials, and that water molecules preferentially dissociate at the surface. The calculated hydroxylated and hydrated surface terminations, as obtained from careful consideration of the charge ordering in the bulk, serve as a strong basis for future studies of the electrical double layer at the mineral -water interface.

Investigation of bio-removing metal ions from wastewater―a viewpoint of micro forces

“…The Fe 3 O 4 ball was considered to be a spherical segment of the lattice-like magnetite [37,38]. The metal ions were represented as the form of free residues, whose force field parameters were adopted from the literature [39,40].…”

Experimental and First‐Principles Characterization of Functionalized Magnetic Nanoparticles

“…Hence, the stability of the functionalized NP translates into surfactant binding avidity to the NP surface and, correspondingly, into the potential modifications brought to the surface itself as a result of particle size. To this extent, magnetic NPs have been reported to assume an oxidized‐like state with an elementary unit cell that is similar to magnetite but includes only Fe 3+ ,18 whereas, in another instance, the magnetite (001) surface has been reported as preferentially terminated by tetrahedral Fe atoms, based on results from charge‐ordered density functional theory (DFT) calculations 19. NP synthesis itself is achieved by an array of methods, including reduction of hematite by CO/CO 2 ,20 coprecipitation from a solution of ferrous/ferric salt mixtures in an alkaline medium,21 hydrolysis,22 sol–gel‐based techniques, and oxidation of Fe(OH) 2 by H 2 O 2 23.…”

New Insights into the Adsorption of Oleate on Cassiterite: A DFT Study

“…Generalised gradient approximation (GGA) and local-density approximation (LDA) are the two favorite types at present. However, because of having inherent problems [25][26][27], LDA is not applicable to metal oxides. Thus, in this work, the five most common GGA functionals were used to optimize the cassiterite unit-cell, and the computed lattice constants were contrasted with those observed in X-ray diffraction to determine the suitable functional.…”