DFT-D2 simulations of water adsorption and dissociation on the low-index surfaces of mackinawite (FeS)

Abstract

The adsorption and dissociation of water on mackinawite (layered FeS) surfaces were studied using dispersion-corrected density functional theory (DFT-D2) calculations. The catalytically active sites for H2O and its dissociated products on the FeS {001}, {011}, {100}, and {111} surfaces were determined, and the reaction energetics and kinetics of water dissociation were calculated using the climbing image nudged elastic band technique. Water and its dissociation products are shown to adsorb more strongly onto the least stable FeS{111} surface, which presents low-coordinated cations in the surface, and weakest onto the most stable FeS{001} surface. The adsorption energies decrease in the order FeS{111} > FeS{100} > FeS{011} > FeS{001}. Consistent with the superior reactivity of the FeS{111} surface towards water and its dissociation products, our calculated thermochemical energies and activation barriers suggest that the water dissociation reaction will take place preferentially on the FeS nanoparticle surface with the {111} orientation. These findings improve our understanding of how the different FeS surface structures and the relative stabilities dictate their reactivity towards water adsorption and dissociation.

Structures and Properties of As(OH)3 Adsorption Complexes on Hydrated Mackinawite (FeS) Surfaces: A DFT-D2 Study

“…All the FeS surfaces were stabilized through hydration, as is perhaps to be expected because the adsorbed water molecules stabilize the low-coordinated surface atoms. At the FeS(001) surface, we found that the water molecules were only physisorbed with the hydrogen atoms pointing toward the terminating surface sulfur ions (Figure 2a), similar to results obtained from previous DFT, 53,62 and molecular dynamics (MD) simulations 65 of the structure and dynamics of water at the FeS(001) surface. The shortest H–S distance is calculated at 2.319 Å, which is larger than the typical hydrogen-bond length in water of 1.97 Å, 66 and therefore suggests that dispersion forces may play an important role in stabilizing the water molecule on the FeS(001) surface.…”

“…In a previous study, we showed that the dispersion interactions contribute approximately 87% of the total adsorption energy of water on the FeS(001). 62 The average hydrogen to oxygen (H---O) interatomic distance between the water molecules on the (001) surface is calculated at 1.824 Å.…”

Surface and shape modification of mackinawite (FeS) nanocrystals by cysteine adsorption: a first-principles DFT-D2 study

“…[76][77][78] Long-range dispersion forces were accounted for in our calcula-tions using the DFT-D2 approach of Grimme, 79 which is essential for an accurate description of the FeS interlayer interactions, as well as the interactions between the cysteine and FeS surfaces. 33,34,80 The electronic exchange-correlation potential was calculated using the generalized gradient approximation (GGA), with the PW91 functional. 81,82 The inter-actions between the valence electrons and the core were described with the projected augmented wave (PAW) method 83 in the implementation of Kresse and Joubert.…”

“…Mackinawite (FeS) and greigite (Fe3S4) are increasingly considered to be the pre-biotic catalysts for a series of biochemical reactions that occur in hydrothermal systems, making them relevant to the origin of life theories. [32][33][34][35][49][50][51] Experimentally, it is often difficult to determine the funda-mental interactions that take place between surfaces and the functional groups of the surfactants, which are thought to be the main contributing factors in the capping process. 20 However, using simulation techniques capable of modelling the structure of mineral surfaces at the atomic level, it is possible to study computationally the interactions between the crystal surface and the adsorbates.…”

Periodic DFT+U investigation of the bulk and surface properties of marcasite (FeS2)

“…26 There also exist significant information in the literature on the oxidation and chemistry of different stoichiometric and defective pyrite surfaces using ab initio theoretical calculations 27−31 and experimental 32−34 investigations. Hydration and early oxidation of the surfaces of mackinawite, 35,36 greigite, 37,38 and violarite (FeNi2S4) 39 have also been investigated using DFT calculations. However, to date, no systematic theoretical study has been conducted to investigate the structures and stabilities of the major surfaces of marcasite, which makes this investigation timely.…”